Authentication of a client device based on entropy from a server or other device

ABSTRACT

Methods and systems for authenticating a client device using entropy provided by a server and/or a device paired with the client device are described herein. The system may generate static entropy and time-limited entropy based on data from the server and/or the paired device. The static and time-limited entropy may be used to authenticate the client device (application or a user of the client device) in addition to authentication credentials or entropy such as a PIN or password provided by the user. The time-limited entropy may have an expiration time. If the time-limited entropy is expired, the system may request the user to perform a hard authentication with the server, such as by providing a username, password, and/or optionally a two-factor authentication code, among other information.

FIELD

Aspects described herein generally relate to computer networking, remoteaccess, and computer security. More specifically, aspects describedherein relate to authentication of a client device based on entropy froma server and/or other device, such as a device paired with the clientdevice.

BACKGROUND

Client applications protecting sensitive information typically require auser-supplied PIN to authenticate the user. However, a simple PIN mightnot provide sufficient security. For example, a six-digit numeric PIN atmost provides 10⁶ characters of entropy, which may be used for datasecurity. This may be inadequate to withstand a GPU-based passwordcracking attack.

A PIN Validator may be used to verify that the user has entered thecorrect PIN. Current systems may create a PIN Validator by generating arandom phrase, encrypting the random phrase with a derivative of theuser-supplied PIN, and storing the original random phrase and theencrypted random phrase after hashing each of them a number of times forobfuscation. The PIN validator may be stored on the client device.However, this data security mechanism may be reversed in an offlineattack in a matter of hours.

Additionally, the small amount of entropy provided by the user-suppliedPIN might not be able to be used for cryptographic key derivation.Although key-stretching algorithms exist, the algorithms are notadequate for government and other regulated environments with strictsecurity standards.

SUMMARY

The following presents a simplified summary of various aspects describedherein. This summary is not an extensive overview, and is not intendedto identify key or critical elements or to delineate the scope of theclaims. The following summary merely presents some concepts in asimplified form as an introductory prelude to the more detaileddescription provided below.

To overcome limitations in the prior art described above, and toovercome other limitations that will be apparent upon reading andunderstanding the present specification, aspects described herein aredirected towards a system and method comprising receiving a request froma client device for time-limited entropy generated by a server, whereinthe time-limited entropy comprises an expiration time, and wherein thetime-limited entropy is usable to access a static entropy generated bythe server. The method may comprise determining whether a current timeexceeds the expiration time of the time-limited entropy. If the currenttime does not exceed the expiration time of the time-limited entropy,the time-limited entropy may be sent to the client device. In someaspects, the entropy may be encrypted. For example, the server mayencrypt the time-limited entropy using a public key of the client deviceand send the time-limited entropy encrypted using the public key of theclient device.

The request for the time-limited entropy may be received at the server,and the method may further comprise sending, by the server, a responserequesting the client device to perform a hard authentication if thecurrent time exceeds the expiration time of the time-limited entropy.The hard authentication may comprise providing a username and a passwordor a two-factor authentication code.

The method may further comprise receiving and storing, at a devicepaired with the client device, the time-limited entropy generated by theserver. The request for the time-limited entropy may be received at thedevice paired with the client device. Sending the time-limited entropyto the client device may be performed by the device paired with theclient device. The device paired with the client device may comprise amouse connected to the client device via Bluetooth, Near FieldCommunication, Wi-Fi, or USB.

In some aspects, the method may further comprise generating, by theserver and using the time-limited entropy, a key for the static entropy.The key may be usable to access the static entropy. The method mayfurther comprise encrypting the static entropy using the key for thestatic entropy. The encrypted static entropy may be sent to the clientdevice. Generating the key for the static entropy may use a passcodeprovided by a user at the client device, and the method may comprisegenerating, by the server and using the static entropy generated by theserver, a key for the passcode provided by the user.

Aspects described herein are directed towards a system and methodcomprising receiving, at a client device, a user credential, which maycomprise a passcode. In response to receiving the user credential, theclient device may send, to the server or to a device paired with theclient device, a request for time-limited entropy generated by a server.The time-limited entropy may expire at a predefined time. The clientdevice may receive the time-limited entropy generated by the server. Theclient device may also access a stored user credential based on thetime-limited entropy generated by the server and static entropygenerated by the server. A user of the client device may beauthenticated by comparing the received user credential to the storeduser credential. After authenticating the user of the first clientdevice, the client device may access data stored in a secure vault. Theclient device may also send the data stored in the secure vault to asecond client device. The data stored in the secure vault may be usableby the second client device to access one or more resources accessibleto the first client device.

In some aspects, accessing the stored user credential based on thetime-limited entropy and the static entropy may comprise determining akey for the static entropy based on the time-limited entropy, decryptingthe static entropy using the key for the static entropy, determining akey for the stored user credential based on the decrypted staticentropy, and decrypting the stored user credential using the key for thestored user credential.

In some aspects, accessing the stored user credential based on thetime-limited entropy and the static entropy may comprise determining akey for the static entropy based on the received user credential and thetime-limited entropy, decrypting the static entropy using the key forthe static entropy, determining a key for the stored user credentialbased on the time-limited entropy and the decrypted static entropy, anddecrypting the stored user credential using the key for the stored usercredential.

In some aspects, the method may comprise determining, by the clientdevice, that the time-limited entropy has not expired prior to sendingthe request for the time-limited entropy. In these examples, the requestfor the time-limited entropy may be sent in response to receiving theuser credential and in response to determining that the time-limitedentropy has not expired.

The method may comprise the client device locally storing thetime-limited entropy. The locally stored time-limited entropy may expireat a second predefined time. The client device may fetch the locallystored time-limited entropy in response to receiving the usercredential.

Aspects described herein are directed towards an apparatus comprising aprocessor and memory. The memory may store computer-executableinstructions that, when executed by the processor, cause the apparatusto determine time-limited entropy for a client device, the time-limitedentropy having an expiration time. The apparatus may determine staticentropy for the client device. A key for the static entropy may begenerated using a passcode for a user of the client device and thetime-limited entropy, and the passcode may be usable to authenticate theuser. A key for the passcode may be generated using the time-limitedentropy and the static entropy.

The memory may store additional computer-executable instructions that,when executed by the processor, cause the apparatus to encrypt thestatic entropy using the key for the static entropy. The apparatus mayencrypt the passcode using the generated key for the passcode. Theapparatus may also send the encrypted static entropy and the encryptedpasscode to the client device.

In some aspects, the memory may store additional computer-executableinstructions that, when executed by the processor, cause the apparatusto authenticate a device paired with the client device. The apparatusmay encrypt the time-limited entropy with a key accessible by the clientdevice and send the encrypted time-limited entropy and the expirationtime to the device paired with the client device.

These and additional aspects will be appreciated with the benefit of thedisclosures discussed in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of aspects described herein and theadvantages thereof may be acquired by referring to the followingdescription in consideration of the accompanying drawings, in which likereference numbers indicate like features, and wherein:

FIG. 1 depicts an illustrative computer system architecture that may beused in accordance with one or more illustrative aspects describedherein.

FIG. 2 depicts an illustrative remote-access system architecture thatmay be used in accordance with one or more illustrative aspectsdescribed herein.

FIG. 3 depicts an illustrative virtualized (hypervisor) systemarchitecture that may be used in accordance with one or moreillustrative aspects described herein.

FIG. 4 depicts an illustrative cloud-based system architecture that maybe used in accordance with one or more illustrative aspects describedherein.

FIG. 5 depicts an illustrative enterprise mobility management system.

FIG. 6 depicts another illustrative enterprise mobility managementsystem.

FIG. 7A illustrates an example method of registering a client device inaccordance with one or more illustrative aspects described herein.

FIG. 7B illustrates an example method of creating a PIN in accordancewith one or more illustrative aspects described herein.

FIG. 7C illustrates an example method of a server receiving encrypteddata in accordance with one or more illustrative aspects describedherein.

FIGS. 7D and 7E illustrate an example method of creating an expirationticket in accordance with one or more illustrative aspects describedherein.

FIG. 8A illustrates an example method of validating a client deviceidentifier in accordance with one or more illustrative aspects describedherein.

FIG. 8B illustrates an example method of a client device receiving anexpiration ticket in accordance with one or more illustrative aspectsdescribed herein.

FIGS. 8C and 8D illustrate an example method of verifying a PIN inaccordance with one or more illustrative aspects described herein.

FIG. 8E illustrates an example method of a server handling a clientrequest for time-limited entropy in accordance with one or moreillustrative aspects described herein.

FIG. 9 illustrates an example method of registering a paired device inaccordance with one or more illustrative aspects described herein.

FIG. 10 illustrates an example method of authenticating a client deviceusing a paired device in accordance with one or more illustrativeaspects described herein.

FIG. 11 illustrates an example method of a first device sharingsensitive data with a second device via a paired device in accordancewith one or more illustrative aspects described herein.

FIG. 12 illustrates an example method of a first device sharingsensitive data with a second device via a server in accordance with oneor more illustrative aspects described herein.

DETAILED DESCRIPTION

In the following description of the various embodiments, reference ismade to the accompanying drawings identified above and which form a parthereof, and in which is shown by way of illustration various embodimentsin which aspects described herein may be practiced. It is to beunderstood that other embodiments may be utilized and structural andfunctional modifications may be made without departing from the scopedescribed herein. Various aspects are capable of other embodiments andof being practiced or being carried out in various different ways.

As a general introduction to the subject matter described in more detailbelow, aspects described herein are directed towards a system and methodfor authenticating a client device based on entropy obtained from aserver and/or other device, such as a paired device. The system maygenerate keys, such as cryptographic keys, to unlock data in order toauthenticate the client device, application, and/or user of the clientdevice. Data security may be improved because keys generated from serverentropy and/or paired device entropy may be stronger than keys generatedby a short PIN, such as a 4 digit or 6 digit PIN. During authentication,the client device may receive signed data from the server. The signeddata may comprise a time-limited ticket and an encrypted copy of theuser's passcode, such as a PIN or a password. An alphanumeric passwordmay provide more entropy than a short numeric PIN. A PIN, on the otherhand, may be used more often in government or other regulatedenvironments. A PIN may also be easier to frequently type on a mobiledevice than a password. For the sake of brevity, a user PIN is describedherein for authentication of the user and/or client device. However, apassword (or any other passcode) may be used instead of the PIN forauthentication.

The time-limited ticket included in the signed data may be valid for arange of hours to days (e.g., 24 hours, 72 hours, etc.). If the currenttime is within the ticket validity window, a cryptographic key may beused to decrypt the PIN that is stored at the client device. Thecryptographic key may comprise key material created on the server. ThePIN entered by the user may be compared to the correct PIN toauthenticate the user and/or the client device. Keys may also allow theclient device to unlock encrypted vaults on the client device thatcontain additional passwords, certificates, cookies, and other sensitiveinformation.

It is to be understood that the phraseology and terminology used hereinare for the purpose of description and should not be regarded aslimiting. Rather, the phrases and terms used herein are to be giventheir broadest interpretation and meaning. The use of “including” and“comprising” and variations thereof is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional itemsand equivalents thereof. The use of the terms “mounted,” “connected,”“coupled,” “positioned,” “engaged” and similar terms, is meant toinclude both direct and indirect mounting, connecting, coupling,positioning and engaging.

Computing Architecture

Computer software, hardware, and networks may be utilized in a varietyof different system environments, including standalone, networked,remote-access (aka, remote desktop), virtualized, and/or cloud-basedenvironments, among others. FIG. 1 illustrates one example of a systemarchitecture and data processing device that may be used to implementone or more illustrative aspects described herein in a standalone and/ornetworked environment. Various network nodes 103, 105, 107, and 109 maybe interconnected via a wide area network (WAN) 101, such as theInternet. Other networks may also or alternatively be used, includingprivate intranets, corporate networks, LANs, metropolitan area networks(MAN) wireless networks, personal networks (PAN), and the like. Network101 is for illustration purposes and may be replaced with fewer oradditional computer networks. A local area network (LAN) may have one ormore of any known LAN topology and may use one or more of a variety ofdifferent protocols, such as Ethernet. Devices 103, 105, 107, 109 andother devices (not shown) may be connected to one or more of thenetworks via twisted pair wires, coaxial cable, fiber optics, radiowaves or other communication media.

The term “network” as used herein and depicted in the drawings refersnot only to systems in which remote storage devices are coupled togethervia one or more communication paths, but also to stand-alone devicesthat may be coupled, from time to time, to such systems that havestorage capability. Consequently, the term “network” includes not only a“physical network” but also a “content network,” which is comprised ofthe data—attributable to a single entity—which resides across allphysical networks.

The components may include data server 103, web server 105, and clientcomputers 107, 109. Data server 103 provides overall access, control andadministration of databases and control software for performing one ormore illustrative aspects describe herein. Data server 103 may beconnected to web server 105 through which users interact with and obtaindata as requested. Alternatively, data server 103 may act as a webserver itself and be directly connected to the Internet. Data server 103may be connected to web server 105 through the network 101 (e.g., theInternet), via direct or indirect connection, or via some other network.Users may interact with the data server 103 using remote computers 107,109, e.g., using a web browser to connect to the data server 103 via oneor more externally exposed web sites hosted by web server 105. Clientcomputers 107, 109 may be used in concert with data server 103 to accessdata stored therein, or may be used for other purposes. For example,from client device 107 a user may access web server 105 using anInternet browser, as is known in the art, or by executing a softwareapplication that communicates with web server 105 and/or data server 103over a computer network (such as the Internet).

Servers and applications may be combined on the same physical machines,and retain separate virtual or logical addresses, or may reside onseparate physical machines. FIG. 1 illustrates just one example of anetwork architecture that may be used, and those of skill in the artwill appreciate that the specific network architecture and dataprocessing devices used may vary, and are secondary to the functionalitythat they provide, as further described herein. For example, servicesprovided by web server 105 and data server 103 may be combined on asingle server.

Each component 103, 105, 107, 109 may be any type of known computer,server, or data processing device. Data server 103, e.g., may include aprocessor 111 controlling overall operation of the rate server 103. Dataserver 103 may further include random access memory (RAM) 113, read onlymemory (ROM) 115, network interface 117, input/output interfaces 119(e.g., keyboard, mouse, display, printer, etc.), and memory 121.Input/output (I/O) 119 may include a variety of interface units anddrives for reading, writing, displaying, and/or printing data or files.Memory 121 may further store operating system software 123 forcontrolling overall operation of the data processing device 103, controllogic 125 for instructing data server 103 to perform aspects describedherein, and other application software 127 providing secondary, support,and/or other functionality which may or might not be used in conjunctionwith aspects described herein. The control logic may also be referred toherein as the data server software 125. Functionality of the data serversoftware may refer to operations or decisions made automatically basedon rules coded into the control logic, made manually by a user providinginput into the system, and/or a combination of automatic processingbased on user input (e.g., queries, data updates, etc.).

Memory 121 may also store data used in performance of one or moreaspects described herein, including a first database 129 and a seconddatabase 131. In some embodiments, the first database may include thesecond database (e.g., as a separate table, report, etc.). That is, theinformation can be stored in a single database, or separated intodifferent logical, virtual, or physical databases, depending on systemdesign. Devices 105, 107, 109 may have similar or different architectureas described with respect to device 103. Those of skill in the art willappreciate that the functionality of data processing device 103 (ordevice 105, 107, 109) as described herein may be spread across multipledata processing devices, for example, to distribute processing loadacross multiple computers, to segregate transactions based on geographiclocation, user access level, quality of service (QoS), etc.

One or more aspects may be embodied in computer-usable or readable dataand/or computer-executable instructions, such as in one or more programmodules, executed by one or more computers or other devices as describedherein. Generally, program modules include routines, programs, objects,components, data structures, etc. that perform particular tasks orimplement particular abstract data types when executed by a processor ina computer or other device. The modules may be written in a source codeprogramming language that is subsequently compiled for execution, or maybe written in a scripting language such as (but not limited to)HyperText Markup Language (HTML) or Extensible Markup Language (XML).The computer executable instructions may be stored on a computerreadable medium such as a nonvolatile storage device. Any suitablecomputer readable storage media may be utilized, including hard disks,CD-ROMs, optical storage devices, magnetic storage devices, and/or anycombination thereof. In addition, various transmission (non-storage)media representing data or events as described herein may be transferredbetween a source and a destination in the form of electromagnetic wavestraveling through signal-conducting media such as metal wires, opticalfibers, and/or wireless transmission media (e.g., air and/or space).Various aspects described herein may be embodied as a method, a dataprocessing system, or a computer program product. Therefore, variousfunctionalities may be embodied in whole or in part in software,firmware and/or hardware or hardware equivalents such as integratedcircuits, field programmable gate arrays (FPGA), and the like.Particular data structures may be used to more effectively implement oneor more aspects described herein, and such data structures arecontemplated within the scope of computer executable instructions andcomputer-usable data described herein.

With further reference to FIG. 2, one or more aspects described hereinmay be implemented in a remote-access environment. FIG. 2 depicts anexample system architecture including a generic computing device 201 inan illustrative computing environment 200 that may be used according toone or more illustrative aspects described herein. Generic computingdevice 201 may be used as a server 206 a in a single-server ormulti-server desktop virtualization system (e.g., a remote access orcloud system) configured to provide virtual machines for client accessdevices. The generic computing device 201 may have a processor 203 forcontrolling overall operation of the server and its associatedcomponents, including RAM 205, ROM 207, I/O module 209, and memory 215.

I/O module 209 may include a mouse, keypad, touch screen, scanner,optical reader, and/or stylus (or other input device(s)) through which auser of generic computing device 201 may provide input, and may alsoinclude one or more of a speaker for providing audio output and a videodisplay device for providing textual, audiovisual, and/or graphicaloutput. Software may be stored within memory 215 and/or other storage toprovide instructions to processor 203 for configuring generic computingdevice 201 into a special purpose computing device in order to performvarious functions as described herein. For example, memory 215 may storesoftware used by the computing device 201, such as an operating system217, application programs 219, and an associated database 221.

Computing device 201 may operate in a networked environment supportingconnections to one or more remote computers, such as terminals 240 (alsoreferred to as client devices). The terminals 240 may be personalcomputers, mobile devices, laptop computers, tablets, or servers thatinclude many or all of the elements described above with respect to thegeneric computing device 103 or 201. The network connections depicted inFIG. 2 include a local area network (LAN) 225 and a wide area network(WAN) 229, but may also include other networks. When used in a LANnetworking environment, computing device 201 may be connected to the LAN225 through a network interface or adapter 223. When used in a WANnetworking environment, computing device 201 may include a modem 227 orother wide area network interface for establishing communications overthe WAN 229, such as computer network 230 (e.g., the Internet). It willbe appreciated that the network connections shown are illustrative andother means of establishing a communications link between the computersmay be used. Computing device 201 and/or terminals 240 may also bemobile terminals (e.g., mobile phones, smartphones, personal digitalassistants (PDAs), notebooks, etc.) including various other components,such as a battery, speaker, and antennas (not shown).

Aspects described herein may also be operational with numerous othergeneral purpose or special purpose computing system environments orconfigurations. Examples of other computing systems, environments,and/or configurations that may be suitable for use with aspectsdescribed herein include, but are not limited to, personal computers,server computers, hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network personal computers (PCs), minicomputers, mainframecomputers, distributed computing environments that include any of theabove systems or devices, and the like.

As shown in FIG. 2, one or more client devices 240 may be incommunication with one or more servers 206 a-206 n (generally referredto herein as “server(s) 206”). In one embodiment, the computingenvironment 200 may include a network appliance installed between theserver(s) 206 and client machine(s) 240. The network appliance maymanage client/server connections, and in some cases can load balanceclient connections amongst a plurality of backend servers 206.

The client machine(s) 240 may in some embodiments be referred to as asingle client machine 240 or a single group of client machines 240,while server(s) 206 may be referred to as a single server 206 or asingle group of servers 206. In one embodiment a single client machine240 communicates with more than one server 206, while in anotherembodiment a single server 206 communicates with more than one clientmachine 240. In yet another embodiment, a single client machine 240communicates with a single server 206.

A client machine 240 can, in some embodiments, be referenced by any oneof the following non-exhaustive terms: client machine(s); client(s);client computer(s); client device(s); client computing device(s); localmachine; remote machine; client node(s); endpoint(s); or endpointnode(s). The server 206, in some embodiments, may be referenced by anyone of the following non-exhaustive terms: server(s), local machine;remote machine; server farm(s), or host computing device(s).

In one embodiment, the client machine 240 may be a virtual machine. Thevirtual machine may be any virtual machine, while in some embodimentsthe virtual machine may be any virtual machine managed by a Type 1 orType 2 hypervisor, for example, a hypervisor developed by CitrixSystems, IBM, VMware, or any other hypervisor. In some aspects, thevirtual machine may be managed by a hypervisor, while in aspects thevirtual machine may be managed by a hypervisor executing on a server 206or a hypervisor executing on a client 240.

Some embodiments include a client device 240 that displays applicationoutput generated by an application remotely executing on a server 206 orother remotely located machine. In these embodiments, the client device240 may execute a virtual machine receiver program or application todisplay the output in an application window, a browser, or other outputwindow. In one example, the application is a desktop, while in otherexamples the application is an application that generates or presents adesktop. A desktop may include a graphical shell providing a userinterface for an instance of an operating system in which local and/orremote applications can be integrated. Applications, as used herein, areprograms that execute after an instance of an operating system (and,optionally, also the desktop) has been loaded.

The server 206, in some embodiments, uses a remote presentation protocolor other program to send data to a thin-client or remote-displayapplication executing on the client to present display output generatedby an application executing on the server 206. The thin-client orremote-display protocol can be any one of the following non-exhaustivelist of protocols: the Independent Computing Architecture (ICA) protocoldeveloped by Citrix Systems, Inc. of Ft. Lauderdale, Fla.; or the RemoteDesktop Protocol (RDP) manufactured by the Microsoft Corporation ofRedmond, Wash.

A remote computing environment may include more than one server 206a-206 n such that the servers 206 a-206 n are logically grouped togetherinto a server farm 206, for example, in a cloud computing environment.The server farm 206 may include servers 206 that are geographicallydispersed while and logically grouped together, or servers 206 that arelocated proximate to each other while logically grouped together.Geographically dispersed servers 206 a-206 n within a server farm 206can, in some embodiments, communicate using a WAN (wide), MAN(metropolitan), or LAN (local), where different geographic regions canbe characterized as: different continents; different regions of acontinent; different countries; different states; different cities;different campuses; different rooms; or any combination of the precedinggeographical locations. In some embodiments the server farm 206 may beadministered as a single entity, while in other embodiments the serverfarm 206 can include multiple server farms.

In some embodiments, a server farm may include servers 206 that executea substantially similar type of operating system platform (e.g.,WINDOWS, UNIX, LINUX, iOS, ANDROID, SYMBIAN, etc.) In other embodiments,server farm 206 may include a first group of one or more servers thatexecute a first type of operating system platform, and a second group ofone or more servers that execute a second type of operating systemplatform.

Server 206 may be configured as any type of server, as needed, e.g., afile server, an application server, a web server, a proxy server, anappliance, a network appliance, a gateway, an application gateway, agateway server, a virtualization server, a deployment server, a SecureSockets Layer (SSL) VPN server, a firewall, a web server, an applicationserver or as a master application server, a server executing an activedirectory, or a server executing an application acceleration programthat provides firewall functionality, application functionality, or loadbalancing functionality. Other server types may also be used.

Some embodiments include a first server 106 a that receives requestsfrom a client machine 240, forwards the request to a second server 106b, and responds to the request generated by the client machine 240 witha response from the second server 106 b. First server 106 a may acquirean enumeration of applications available to the client machine 240 andwell as address information associated with an application server 206hosting an application identified within the enumeration ofapplications. First server 106 a can then present a response to theclient's request using a web interface, and communicate directly withthe client 240 to provide the client 240 with access to an identifiedapplication. One or more clients 240 and/or one or more servers 206 maytransmit data over network 230, e.g., network 101.

FIG. 2 shows a high-level architecture of an illustrative desktopvirtualization system. As shown, the desktop virtualization system maybe single-server or multi-server system, or cloud system, including atleast one virtualization server 206 configured to provide virtualdesktops and/or virtual applications to one or more client accessdevices 240. As used herein, a desktop refers to a graphical environmentor space in which one or more applications may be hosted and/orexecuted. A desktop may include a graphical shell providing a userinterface for an instance of an operating system in which local and/orremote applications can be integrated. Applications may include programsthat execute after an instance of an operating system (and, optionally,also the desktop) has been loaded. Each instance of the operating systemmay be physical (e.g., one operating system per device) or virtual(e.g., many instances of an OS running on a single device). Eachapplication may be executed on a local device, or executed on a remotelylocated device (e.g., remoted).

With further reference to FIG. 3, a computer device 301 may beconfigured as a virtualization server in a virtualization environment,for example, a single-server, multi-server, or cloud computingenvironment. Virtualization server 301 illustrated in FIG. 3 can bedeployed as and/or implemented by one or more embodiments of the server206 illustrated in FIG. 2 or by other known computing devices. Includedin virtualization server 301 is a hardware layer that can include one ormore physical disks 304, one or more physical devices 306, one or morephysical processors 308 and one or more physical memories 316. In someembodiments, firmware 312 can be stored within a memory element in thephysical memory 316 and can be executed by one or more of the physicalprocessors 308. Virtualization server 301 may further include anoperating system 314 that may be stored in a memory element in thephysical memory 316 and executed by one or more of the physicalprocessors 308. Still further, a hypervisor 302 may be stored in amemory element in the physical memory 316 and can be executed by one ormore of the physical processors 308.

Executing on one or more of the physical processors 308 may be one ormore virtual machines 332A-C (generally 332). Each virtual machine 332may have a virtual disk 326A-C and a virtual processor 328A-C. In someembodiments, a first virtual machine 332A may execute, using a virtualprocessor 328A, a control program 320 that includes a tools stack 324.Control program 320 may be referred to as a control virtual machine,Dom0, Domain 0, or other virtual machine used for system administrationand/or control. In some embodiments, one or more virtual machines 332B-Ccan execute, using a virtual processor 328B-C, a guest operating system330A-B.

Virtualization server 301 may include a hardware layer 310 with one ormore pieces of hardware that communicate with the virtualization server301. In some embodiments, the hardware layer 310 can include one or morephysical disks 304, one or more physical devices 306, one or morephysical processors 308, and one or more memory 216. Physical components304, 306, 308, and 316 may include, for example, any of the componentsdescribed above. Physical devices 306 may include, for example, anetwork interface card, a video card, a keyboard, a mouse, an inputdevice, a monitor, a display device, speakers, an optical drive, astorage device, a universal serial bus connection, a printer, a scanner,a network element (e.g., router, firewall, network address translator,load balancer, virtual private network (VPN) gateway, Dynamic HostConfiguration Protocol (DHCP) router, etc.), or any device connected toor communicating with virtualization server 301. Physical memory 316 inthe hardware layer 310 may include any type of memory. Physical memory316 may store data, and in some embodiments may store one or moreprograms, or set of executable instructions. FIG. 3 illustrates anembodiment where firmware 312 is stored within the physical memory 316of virtualization server 301. Programs or executable instructions storedin the physical memory 316 can be executed by the one or more processors308 of virtualization server 301.

Virtualization server 301 may also include a hypervisor 302. In someembodiments, hypervisor 302 may be a program executed by processors 308on virtualization server 301 to create and manage any number of virtualmachines 332. Hypervisor 302 may be referred to as a virtual machinemonitor, or platform virtualization software. In some embodiments,hypervisor 302 can be any combination of executable instructions andhardware that monitors virtual machines executing on a computingmachine. Hypervisor 302 may be Type 2 hypervisor, where the hypervisorthat executes within an operating system 314 executing on thevirtualization server 301. Virtual machines then execute at a levelabove the hypervisor. In some embodiments, the Type 2 hypervisorexecutes within the context of a user's operating system such that theType 2 hypervisor interacts with the user's operating system. In otherembodiments, one or more virtualization servers 201 in a virtualizationenvironment may instead include a Type 1 hypervisor (not shown). A Type1 hypervisor may execute on the virtualization server 301 by directlyaccessing the hardware and resources within the hardware layer 310. Thatis, while a Type 2 hypervisor 302 accesses system resources through ahost operating system 314, as shown, a Type 1 hypervisor may directlyaccess all system resources without the host operating system 314. AType 1 hypervisor may execute directly on one or more physicalprocessors 308 of virtualization server 301, and may include programdata stored in the physical memory 316.

Hypervisor 302, in some embodiments, can provide virtual resources tooperating systems 330 or control programs 320 executing on virtualmachines 332 in any manner that simulates the operating systems 330 orcontrol programs 320 having direct access to system resources. Systemresources can include, but are not limited to, physical devices 306,physical disks 304, physical processors 308, physical memory 316 and anyother component included in virtualization server 301 hardware layer310. Hypervisor 302 may be used to emulate virtual hardware, partitionphysical hardware, virtualize physical hardware, and/or execute virtualmachines that provide access to computing environments. In still otherembodiments, hypervisor 302 controls processor scheduling and memorypartitioning for a virtual machine 332 executing on virtualizationserver 301. Hypervisor 302 may include those manufactured by VMWare,Inc., of Palo Alto, Calif.; the XEN hypervisor, an open source productwhose development is overseen by the open source Xen.org community;HyperV, VirtualServer or virtual PC hypervisors provided by Microsoft,or others. In some embodiments, virtualization server 301 executes ahypervisor 302 that creates a virtual machine platform on which guestoperating systems may execute. In these embodiments, the virtualizationserver 301 may be referred to as a host server. An example of such avirtualization server is the XEN SERVER provided by Citrix Systems,Inc., of Fort Lauderdale, Fla.

Hypervisor 302 may create one or more virtual machines 332B-C (generally332) in which guest operating systems 330 execute. In some embodiments,hypervisor 302 may load a virtual machine image to create a virtualmachine 332. In other embodiments, the hypervisor 302 may executes aguest operating system 330 within virtual machine 332. In still otherembodiments, virtual machine 332 may execute guest operating system 330.

In addition to creating virtual machines 332, hypervisor 302 may controlthe execution of at least one virtual machine 332. In other embodiments,hypervisor 302 may presents at least one virtual machine 332 with anabstraction of at least one hardware resource provided by thevirtualization server 301 (e.g., any hardware resource available withinthe hardware layer 310). In other embodiments, hypervisor 302 maycontrol the manner in which virtual machines 332 access physicalprocessors 308 available in virtualization server 301. Controllingaccess to physical processors 308 may include determining whether avirtual machine 332 should have access to a processor 308, and howphysical processor capabilities are presented to the virtual machine332.

As shown in FIG. 3, virtualization server 301 may host or execute one ormore virtual machines 332. A virtual machine 332 is a set of executableinstructions that, when executed by a processor 308, imitate theoperation of a physical computer such that the virtual machine 332 canexecute programs and processes much like a physical computing device.While FIG. 3 illustrates an embodiment where a virtualization server 301hosts three virtual machines 332, in other embodiments virtualizationserver 301 can host any number of virtual machines 332. Hypervisor 302,in some embodiments, provides each virtual machine 332 with a uniquevirtual view of the physical hardware, memory, processor and othersystem resources available to that virtual machine 332. In someembodiments, the unique virtual view can be based on one or more ofvirtual machine permissions, application of a policy engine to one ormore virtual machine identifiers, a user accessing a virtual machine,the applications executing on a virtual machine, networks accessed by avirtual machine, or any other desired criteria. For instance, hypervisor302 may create one or more unsecure virtual machines 332 and one or moresecure virtual machines 332. Unsecure virtual machines 332 may beprevented from accessing resources, hardware, memory locations, andprograms that secure virtual machines 332 may be permitted to access. Inother embodiments, hypervisor 302 may provide each virtual machine 332with a substantially similar virtual view of the physical hardware,memory, processor and other system resources available to the virtualmachines 332.

Each virtual machine 332 may include a virtual disk 326A-C (generally326) and a virtual processor 328A-C (generally 328.) The virtual disk326, in some embodiments, is a virtualized view of one or more physicaldisks 304 of the virtualization server 301, or a portion of one or morephysical disks 304 of the virtualization server 301. The virtualizedview of the physical disks 304 can be generated, provided and managed bythe hypervisor 302. In some embodiments, hypervisor 302 provides eachvirtual machine 332 with a unique view of the physical disks 304. Thus,in these embodiments, the particular virtual disk 326 included in eachvirtual machine 332 can be unique when compared with the other virtualdisks 326.

A virtual processor 328 can be a virtualized view of one or morephysical processors 308 of the virtualization server 301. In someembodiments, the virtualized view of the physical processors 308 can begenerated, provided and managed by hypervisor 302. In some embodiments,virtual processor 328 has substantially all of the same characteristicsof at least one physical processor 308. In other embodiments, virtualprocessor 308 provides a modified view of physical processors 308 suchthat at least some of the characteristics of the virtual processor 328are different than the characteristics of the corresponding physicalprocessor 308.

With further reference to FIG. 4, some aspects described herein may beimplemented in a cloud-based environment. FIG. 4 illustrates an exampleof a cloud computing environment (or cloud system) 400. As seen in FIG.4, client computers 411-414 may communicate with a cloud managementserver 410 to access the computing resources (e.g., host servers 403,storage resources 404, and network resources 405) of the cloud system.

Management server 410 may be implemented on one or more physicalservers. The management server 410 may run, for example, CLOUDSTACK byCitrix Systems, Inc. of Ft. Lauderdale, Fla., or OPENSTACK, amongothers. Management server 410 may manage various computing resources,including cloud hardware and software resources, for example, hostcomputers 403, data storage devices 404, and networking devices 405. Thecloud hardware and software resources may include private and/or publiccomponents. For example, a cloud may be configured as a private cloud tobe used by one or more particular customers or client computers 411-414and/or over a private network. In other embodiments, public clouds orhybrid public-private clouds may be used by other customers over an openor hybrid networks.

Management server 410 may be configured to provide user interfacesthrough which cloud operators and cloud customers may interact with thecloud system. For example, the management server 410 may provide a setof application programming interfaces (APIs) and/or one or more cloudoperator console applications (e.g., web-based on standaloneapplications) with user interfaces to allow cloud operators to managethe cloud resources, configure the virtualization layer, manage customeraccounts, and perform other cloud administration tasks. The managementserver 410 also may include a set of APIs and/or one or more customerconsole applications with user interfaces configured to receive cloudcomputing requests from end users via client computers 411-414, forexample, requests to create, modify, or destroy virtual machines withinthe cloud. Client computers 411-414 may connect to management server 410via the Internet or other communication network, and may request accessto one or more of the computing resources managed by management server410. In response to client requests, the management server 410 mayinclude a resource manager configured to select and provision physicalresources in the hardware layer of the cloud system based on the clientrequests. For example, the management server 410 and additionalcomponents of the cloud system may be configured to provision, create,and manage virtual machines and their operating environments (e.g.,hypervisors, storage resources, services offered by the networkelements, etc.) for customers at client computers 411-414, over anetwork (e.g., the Internet), providing customers with computationalresources, data storage services, networking capabilities, and computerplatform and application support. Cloud systems also may be configuredto provide various specific services, including security systems,development environments, user interfaces, and the like.

Certain clients 411-414 may be related, for example, different clientcomputers creating virtual machines on behalf of the same end user, ordifferent users affiliated with the same company or organization. Inother examples, certain clients 411-414 may be unrelated, such as usersaffiliated with different companies or organizations. For unrelatedclients, information on the virtual machines or storage of any one usermay be hidden from other users.

Referring now to the physical hardware layer of a cloud computingenvironment, availability zones 401-402 (or zones) may refer to acollocated set of physical computing resources. Zones may begeographically separated from other zones in the overall cloud ofcomputing resources. For example, zone 401 may be a first clouddatacenter located in California, and zone 402 may be a second clouddatacenter located in Florida. Management sever 410 may be located atone of the availability zones, or at a separate location. Each zone mayinclude an internal network that interfaces with devices that areoutside of the zone, such as the management server 410, through agateway. End users of the cloud (e.g., clients 411-414) might or mightnot be aware of the distinctions between zones. For example, an end usermay request the creation of a virtual machine having a specified amountof memory, processing power, and network capabilities. The managementserver 410 may respond to the user's request and may allocate theresources to create the virtual machine without the user knowing whetherthe virtual machine was created using resources from zone 401 or zone402. In other examples, the cloud system may allow end users to requestthat virtual machines (or other cloud resources) are allocated in aspecific zone or on specific resources 403-405 within a zone.

In this example, each zone 401-402 may include an arrangement of variousphysical hardware components (or computing resources) 403-405, forexample, physical hosting resources (or processing resources), physicalnetwork resources, physical storage resources, switches, and additionalhardware resources that may be used to provide cloud computing servicesto customers. The physical hosting resources in a cloud zone 401-402 mayinclude one or more computer servers 403, such as the virtualizationservers 301 described above, which may be configured to create and hostvirtual machine instances. The physical network resources in a cloudzone 401 or 402 may include one or more network elements 405 (e.g.,network service providers) comprising hardware and/or softwareconfigured to provide a network service to cloud customers, such asfirewalls, network address translators, load balancers, virtual privatenetwork (VPN) gateways, Dynamic Host Configuration Protocol (DHCP)routers, and the like. The storage resources in the cloud zone 401-402may include storage disks (e.g., solid state drives (SSDs), magnetichard disks, etc.) and other storage devices.

The example cloud computing environment shown in FIG. 4 also may includea virtualization layer (e.g., as shown in FIGS. 1-3) with additionalhardware and/or software resources configured to create and managevirtual machines and provide other services to customers using thephysical resources in the cloud. The virtualization layer may includehypervisors, as described above in FIG. 3, along with other componentsto provide network virtualizations, storage virtualizations, etc. Thevirtualization layer may be as a separate layer from the physicalresource layer, or may share some or all of the same hardware and/orsoftware resources with the physical resource layer. For example, thevirtualization layer may include a hypervisor installed in each of thevirtualization servers 403 with the physical computing resources. Knowncloud systems may alternatively be used, e.g., WINDOWS AZURE (MicrosoftCorporation of Redmond Wash.), AMAZON EC2 (Amazon.com Inc. of Seattle,Wash.), IBM BLUE CLOUD (IBM Corporation of Armonk, N.Y.), or others.

Enterprise Mobility Management Architecture

FIG. 5 represents an enterprise mobility technical architecture 500 foruse in a BYOD environment. The architecture enables a user of a mobiledevice 502 to both access enterprise or personal resources from a mobiledevice 502 and use the mobile device 502 for personal use. The user mayaccess such enterprise resources 504 or enterprise services 508 using amobile device 502 that is purchased by the user or a mobile device 502that is provided by the enterprise to user. The user may utilize themobile device 502 for business use only or for business and personaluse. The mobile device may run an iOS operating system, and Androidoperating system, or the like. The enterprise may choose to implementpolicies to manage the mobile device 504. The policies may be implantedthrough a firewall or gateway in such a way that the mobile device maybe identified, secured or security verified, and provided selective orfull access to the enterprise resources. The policies may be mobiledevice management policies, mobile application management policies,mobile data management policies, or some combination of mobile device,application, and data management policies. A mobile device 504 that ismanaged through the application of mobile device management policies maybe referred to as an enrolled device.

In some embodiments, the operating system of the mobile device may beseparated into a managed partition 510 and an unmanaged partition 512.The managed partition 510 may have policies applied to it to secure theapplications running on and data stored in the managed partition. Theapplications running on the managed partition may be secureapplications. In other embodiments, all applications may execute inaccordance with a set of one or more policy files received separate fromthe application, and which define one or more security parameters,features, resource restrictions, and/or other access controls that areenforced by the mobile device management system when that application isexecuting on the device. By operating in accordance with theirrespective policy file(s), each application may be allowed or restrictedfrom communications with one or more other applications and/orresources, thereby creating a virtual partition. Thus, as used herein, apartition may refer to a physically partitioned portion of memory(physical partition), a logically partitioned portion of memory (logicalpartition), and/or a virtual partition created as a result ofenforcement of one or more policies and/or policy files across multipleapps as described herein (virtual partition). Stated differently, byenforcing policies on managed apps, those apps may be restricted to onlybe able to communicate with other managed apps and trusted enterpriseresources, thereby creating a virtual partition that is impenetrable byunmanaged apps and devices.

The secure applications may be email applications, web browsingapplications, software-as-a-service (SaaS) access applications, WindowsApplication access applications, and the like. The secure applicationsmay be secure native applications 514, secure remote applications 522executed by a secure application launcher 518, virtualizationapplications 526 executed by a secure application launcher 518, and thelike. The secure native applications 514 may be wrapped by a secureapplication wrapper 520. The secure application wrapper 520 may includeintegrated policies that are executed on the mobile device 502 when thesecure native application is executed on the device. The secureapplication wrapper 520 may include meta-data that points the securenative application 514 running on the mobile device 502 to the resourceshosted at the enterprise that the secure native application 514 mayrequire to complete the task requested upon execution of the securenative application 514. The secure remote applications 522 executed by asecure application launcher 518 may be executed within the secureapplication launcher application 518. The virtualization applications526 executed by a secure application launcher 518 may utilize resourceson the mobile device 502, at the enterprise resources 504, and the like.The resources used on the mobile device 502 by the virtualizationapplications 526 executed by a secure application launcher 518 mayinclude user interaction resources, processing resources, and the like.The user interaction resources may be used to collect and transmitkeyboard input, mouse input, camera input, tactile input, audio input,visual input, gesture input, and the like. The processing resources maybe used to present a user interface, process data received from theenterprise resources 504, and the like. The resources used at theenterprise resources 504 by the virtualization applications 526 executedby a secure application launcher 518 may include user interfacegeneration resources, processing resources, and the like. The userinterface generation resources may be used to assemble a user interface,modify a user interface, refresh a user interface, and the like. Theprocessing resources may be used to create information, readinformation, update information, delete information, and the like. Forexample, the virtualization application may record user interactionsassociated with a graphical user interface (GUI) and communicate them toa server application where the server application will use the userinteraction data as an input to the application operating on the server.In this arrangement, an enterprise may elect to maintain the applicationon the server side as well as data, files, etc. associated with theapplication. While an enterprise may elect to “mobilize” someapplications in accordance with the principles herein by securing themfor deployment on the mobile device, this arrangement may also beelected for certain applications. For example, while some applicationsmay be secured for use on the mobile device, others might not beprepared or appropriate for deployment on the mobile device so theenterprise may elect to provide the mobile user access to the unpreparedapplications through virtualization techniques. As another example, theenterprise may have large complex applications with large and complexdata sets (e.g., material resource planning applications) where it wouldbe very difficult, or otherwise undesirable, to customize theapplication for the mobile device so the enterprise may elect to provideaccess to the application through virtualization techniques. As yetanother example, the enterprise may have an application that maintainshighly secured data (e.g., human resources data, customer data,engineering data) that may be deemed by the enterprise as too sensitivefor even the secured mobile environment so the enterprise may elect touse virtualization techniques to permit mobile access to suchapplications and data. An enterprise may elect to provide both fullysecured and fully functional applications on the mobile device as wellas a virtualization application to allow access to applications that aredeemed more properly operated on the server side. In an embodiment, thevirtualization application may store some data, files, etc. on themobile phone in one of the secure storage locations. An enterprise, forexample, may elect to allow certain information to be stored on thephone while not permitting other information.

In connection with the virtualization application, as described herein,the mobile device may have a virtualization application that is designedto present GUIs and then record user interactions with the GUI. Theapplication may communicate the user interactions to the server side tobe used by the server side application as user interactions with theapplication. In response, the application on the server side maytransmit back to the mobile device a new GUI. For example, the new GUImay be a static page, a dynamic page, an animation, or the like, therebyproviding access to remotely located resources.

The secure applications may access data stored in a secure datacontainer 528 in the managed partition 510 of the mobile device. Thedata secured in the secure data container may be accessed by the securewrapped applications 514, applications executed by a secure applicationlauncher 522, virtualization applications 526 executed by a secureapplication launcher 522, and the like. The data stored in the securedata container 528 may include files, databases, and the like. The datastored in the secure data container 528 may include data restricted to aspecific secure application 530, shared among secure applications 532,and the like. Data restricted to a secure application may include securegeneral data 534 and highly secure data 538. Secure general data may usea strong form of encryption such as Advanced Encryption Standard (AES)128-bit encryption or the like, while highly secure data 538 may use avery strong form of encryption such as AES 256-bit encryption. Datastored in the secure data container 528 may be deleted from the deviceupon receipt of a command from the device manager 524. The secureapplications may have a dual-mode option 540. The dual mode option 540may present the user with an option to operate the secured applicationin an unsecured or unmanaged mode. In an unsecured or unmanaged mode,the secure applications may access data stored in an unsecured datacontainer 542 on the unmanaged partition 512 of the mobile device 502.The data stored in an unsecured data container may be personal data 544.The data stored in an unsecured data container 542 may also be accessedby unsecured applications 548 that are running on the unmanagedpartition 512 of the mobile device 502. The data stored in an unsecureddata container 542 may remain on the mobile device 502 when the datastored in the secure data container 528 is deleted from the mobiledevice 502. An enterprise may want to delete from the mobile deviceselected or all data, files, and/or applications owned, licensed orcontrolled by the enterprise (enterprise data) while leaving orotherwise preserving personal data, files, and/or applications owned,licensed or controlled by the user (personal data). This operation maybe referred to as a selective wipe. With the enterprise and personaldata arranged in accordance to the aspects described herein, anenterprise may perform a selective wipe.

The mobile device may connect to enterprise resources 504 and enterpriseservices 508 at an enterprise, to the public Internet 548, and the like.The mobile device may connect to enterprise resources 504 and enterpriseservices 508 through virtual private network connections. The virtualprivate network connections, also referred to as microVPN orapplication-specific VPN, may be specific to particular applications550, particular devices, particular secured areas on the mobile device,and the like 552. For example, each of the wrapped applications in thesecured area of the phone may access enterprise resources through anapplication specific VPN such that access to the VPN would be grantedbased on attributes associated with the application, possibly inconjunction with user or device attribute information. The virtualprivate network connections may carry Microsoft Exchange traffic,Microsoft Active Directory traffic, HyperText Transfer Protocol (HTTP)traffic, HyperText Transfer Protocol Secure (HTTPS) traffic, applicationmanagement traffic, and the like. The virtual private networkconnections may support and enable single-sign-on authenticationprocesses 554. The single-sign-on processes may allow a user to providea single set of authentication credentials, which are then verified byan authentication service 558. The authentication service 558 may thengrant to the user access to multiple enterprise resources 504, withoutrequiring the user to provide authentication credentials to eachindividual enterprise resource 504.

The virtual private network connections may be established and managedby an access gateway 560. The access gateway 560 may include performanceenhancement features that manage, accelerate, and improve the deliveryof enterprise resources 504 to the mobile device 502. The access gatewaymay also re-route traffic from the mobile device 502 to the publicInternet 548, enabling the mobile device 502 to access publiclyavailable and unsecured applications that run on the public Internet548. The mobile device may connect to the access gateway via a transportnetwork 562. The transport network 562 may be a wired network, wirelessnetwork, cloud network, local area network, metropolitan area network,wide area network, public network, private network, and the like.

The enterprise resources 504 may include email servers, file sharingservers, SaaS applications, Web application servers, Windows applicationservers, and the like. Email servers may include Exchange servers, LotusNotes servers, and the like. File sharing servers may include ShareFileservers, and the like. SaaS applications may include Salesforce, and thelike. Windows application servers may include any application serverthat is built to provide applications that are intended to run on alocal Windows operating system, and the like. The enterprise resources504 may be premise-based resources, cloud based resources, and the like.The enterprise resources 504 may be accessed by the mobile device 502directly or through the access gateway 560. The enterprise resources 504may be accessed by the mobile device 502 via a transport network 562.The transport network 562 may be a wired network, wireless network,cloud network, local area network, metropolitan area network, wide areanetwork, public network, private network, and the like.

The enterprise services 508 may include authentication services 558,threat detection services 564, device manager services 524, file sharingservices 568, policy manager services 570, social integration services572, application controller services 574, and the like. Authenticationservices 558 may include user authentication services, deviceauthentication services, application authentication services, dataauthentication services and the like. Authentication services 558 mayuse certificates. The certificates may be stored on the mobile device502, by the enterprise resources 504, and the like. The certificatesstored on the mobile device 502 may be stored in an encrypted locationon the mobile device, the certificate may be temporarily stored on themobile device 502 for use at the time of authentication, and the like.Threat detection services 564 may include intrusion detection services,unauthorized access attempt detection services, and the like.Unauthorized access attempt detection services may include unauthorizedattempts to access devices, applications, data, and the like. Devicemanagement services 524 may include configuration, provisioning,security, support, monitoring, reporting, and decommissioning services.File sharing services 568 may include file management services, filestorage services, file collaboration services, and the like. Policymanager services 570 may include device policy manager services,application policy manager services, data policy manager services, andthe like. Social integration services 572 may include contactintegration services, collaboration services, integration with socialnetworks such as Facebook, Twitter, and LinkedIn, and the like.Application controller services 574 may include management services,provisioning services, deployment services, assignment services,revocation services, wrapping services, and the like.

The enterprise mobility technical architecture 500 may include anapplication store 578. The application store 578 may include unwrappedapplications 580, pre-wrapped applications 582, and the like.Applications may be populated in the application store 578 from theapplication controller 574. The application store 578 may be accessed bythe mobile device 502 through the access gateway 560, through the publicInternet 548, or the like. The application store may be provided with anintuitive and easy to use User Interface.

A software development kit 584 may provide a user the capability tosecure applications selected by the user by wrapping the application asdescribed previously in this description. An application that has beenwrapped using the software development kit 584 may then be madeavailable to the mobile device 502 by populating it in the applicationstore 578 using the application controller 574.

The enterprise mobility technical architecture 500 may include amanagement and analytics capability 588. The management and analyticscapability 588 may provide information related to how resources areused, how often resources are used, and the like. Resources may includedevices, applications, data, and the like. How resources are used mayinclude which devices download which applications, which applicationsaccess which data, and the like. How often resources are used mayinclude how often an application has been downloaded, how many times aspecific set of data has been accessed by an application, and the like.

FIG. 6 is another illustrative enterprise mobility management system600. Some of the components of the mobility management system 500described above with reference to FIG. 5 have been omitted for the sakeof simplicity. The architecture of the system 600 depicted in FIG. 6 issimilar in many respects to the architecture of the system 500 describedabove with reference to FIG. 5 and may include additional features notmentioned above.

In this case, the left hand side represents an enrolled mobile device602 with a client agent 604, which interacts with gateway server 606(which includes Access Gateway and application controller functionality)to access various enterprise resources 608 and services 609 such asExchange, Sharepoint, public-key infrastructure (PKI) Resources,Kerberos Resources, Certificate Issuance service, as shown on the righthand side above. Although not specifically shown, the mobile device 602may also interact with an enterprise application store (StoreFront) forthe selection and downloading of applications.

The client agent 604 acts as the UI (user interface) intermediary forWindows apps/desktops hosted in an Enterprise data center, which areaccessed using the High-Definition User Experience (HDX)/ICA displayremoting protocol. The client agent 604 also supports the installationand management of native applications on the mobile device 602, such asnative iOS or Android applications. For example, the managedapplications 610 (mail, browser, wrapped application) shown in thefigure above are all native applications that execute locally on thedevice. Client agent 604 and application management framework of thisarchitecture act to provide policy driven management capabilities andfeatures such as connectivity and SSO (single sign on) to enterpriseresources/services 608. The client agent 604 handles primary userauthentication to the enterprise, normally to Access Gateway (AG) withSSO to other gateway server components. The client agent 604 obtainspolicies from gateway server 606 to control the behavior of the managedapplications 610 on the mobile device 602.

The secure interprocess communication (IPC) links 612 between the nativeapplications 610 and client agent 604 represent a management channel,which allows client agent to supply policies to be enforced by theapplication management framework 614 “wrapping” each application. TheIPC channel 612 also allows client agent 604 to supply credential andauthentication information that enables connectivity and SSO toenterprise resources 608. Finally the IPC channel 612 allows theapplication management framework 614 to invoke user interface functionsimplemented by client agent 604, such as online and offlineauthentication.

Communications between the client agent 604 and gateway server 606 areessentially an extension of the management channel from the applicationmanagement framework 614 wrapping each native managed application 610.The application management framework 614 requests policy informationfrom client agent 604, which in turn requests it from gateway server606. The application management framework 614 requests authentication,and client agent 604 logs into the gateway services part of gatewayserver 606 (also known as NetScaler Access Gateway). Client agent 604may also call supporting services on gateway server 606, which mayproduce input material to derive encryption keys for the local datavaults 616, or provide client certificates which may enable directauthentication to PKI protected resources, as more fully explainedbelow.

In more detail, the application management framework 614 “wraps” eachmanaged application 610. This may be incorporated via an explicit buildstep, or via a post-build processing step. The application managementframework 614 may “pair” with client agent 604 on first launch of anapplication 610 to initialize the Secure IPC channel and obtain thepolicy for that application. The application management framework 614may enforce relevant portions of the policy that apply locally, such asthe client agent login dependencies and some of the containment policiesthat restrict how local OS services may be used, or how they mayinteract with the application 610.

The application management framework 614 may use services provided byclient agent 604 over the Secure IPC channel 612 to facilitateauthentication and internal network access. Key management for theprivate and shared data vaults 616 (containers) may be also managed byappropriate interactions between the managed applications 610 and clientagent 604. Vaults 616 may be available only after online authentication,or may be made available after offline authentication if allowed bypolicy. First use of vaults 616 may require online authentication, andoffline access may be limited to at most the policy refresh periodbefore online authentication is again required.

Network access to internal resources may occur directly from individualmanaged applications 610 through Access Gateway 606. The applicationmanagement framework 614 is responsible for orchestrating the networkaccess on behalf of each application 610. Client agent 604 mayfacilitate these network connections by providing suitable time limitedsecondary credentials obtained following online authentication. Multiplemodes of network connection may be used, such as reverse web proxyconnections and end-to-end VPN-style tunnels 618.

The Mail and Browser managed applications 610 have special status andmay make use of facilities that might not be generally available toarbitrary wrapped applications. For example, the Mail application mayuse a special background network access mechanism that allows it toaccess Exchange over an extended period of time without requiring a fullAG logon. The Browser application may use multiple private data vaultsto segregate different kinds of data.

This architecture supports the incorporation of various other securityfeatures. For example, gateway server 606 (including its gatewayservices) in some cases will not need to validate active directory (AD)passwords. It can be left to the discretion of an enterprise whether anAD password is used as an authentication factor for some users in somesituations. Different authentication methods may be used if a user isonline or offline (i.e., connected or not connected to a network).

Step up authentication is a feature wherein gateway server 606 mayidentify managed native applications 610 that are allowed to have accessto highly classified data requiring strong authentication, and ensurethat access to these applications is only permitted after performingappropriate authentication, even if this means a re-authentication isrequired by the user after a prior weaker level of login.

Another security feature of this solution is the encryption of the datavaults 616 (containers) on the mobile device 602. The vaults 616 may beencrypted so that all on-device data including files, databases, andconfigurations are protected. For on-line vaults, the keys may be storedon the server (gateway server 606), and for off-line vaults, a localcopy of the keys may be protected by a user password or biometricvalidation. When data is stored locally on the device 602 in the securecontainer 616, it is preferred that a minimum of AES 256 encryptionalgorithm be utilized.

Other secure container features may also be implemented. For example, alogging feature may be included, wherein all security events happeninginside an application 610 are logged and reported to the backend. Datawiping may be supported, such as if the application 610 detectstampering, associated encryption keys may be written over with randomdata, leaving no hint on the file system that user data was destroyed.Screenshot protection is another feature, where an application mayprevent any data from being stored in screenshots. For example, the keywindow's hidden property may be set to YES. This may cause whatevercontent is currently displayed on the screen to be hidden, resulting ina blank screenshot where any content would normally reside.

Local data transfer may be prevented, such as by preventing any datafrom being locally transferred outside the application container, e.g.,by copying it or sending it to an external application. A keyboard cachefeature may operate to disable the autocorrect functionality forsensitive text fields. SSL certificate validation may be operable so theapplication specifically validates the server SSL certificate instead ofit being stored in the keychain. An encryption key generation featuremay be used such that the key used to encrypt data on the device isgenerated using a passphrase or biometric data supplied by the user (ifoffline access is required). It may be XORed with another key randomlygenerated and stored on the server side if offline access is notrequired. Key Derivation functions may operate such that keys generatedfrom the user password use KDFs (key derivation functions, notablyPassword-Based Key Derivation Function 2 (PBKDF2)) rather than creatinga cryptographic hash of it. The latter makes a key susceptible to bruteforce or dictionary attacks.

Further, one or more initialization vectors may be used in encryptionmethods. An initialization vector will cause multiple copies of the sameencrypted data to yield different cipher text output, preventing bothreplay and cryptanalytic attacks. This will also prevent an attackerfrom decrypting any data even with a stolen encryption key if thespecific initialization vector used to encrypt the data is not known.Further, authentication then decryption may be used, wherein applicationdata is decrypted only after the user has authenticated within theapplication. Another feature may relate to sensitive data in memory,which may be kept in memory (and not in disk) only when it's needed. Forexample, login credentials may be wiped from memory after login, andencryption keys and other data inside objective-C instance variables arenot stored, as they may be easily referenced. Instead, memory may bemanually allocated for these.

An inactivity timeout may be implemented, wherein after a policy-definedperiod of inactivity, a user session is terminated.

Data leakage from the application management framework 614 may beprevented in other ways. For example, when an application 610 is put inthe background, the memory may be cleared after a predetermined(configurable) time period. When backgrounded, a snapshot may be takenof the last displayed screen of the application to fasten theforegrounding process. The screenshot may contain confidential data andhence should be cleared.

Another security feature relates to the use of an OTP (one timepassword) 620 without the use of an AD (active directory) 622 passwordfor access to one or more applications. In some cases, some users do notknow (or are not permitted to know) their AD password, so these usersmay authenticate using an OTP 620 such as by using a hardware OTP systemlike SecurID (OTPs may be provided by different vendors also, such asEntrust or Gemalto). In some cases, after a user authenticates with auser ID, a text is sent to the user with an OTP 620. In some cases, thismay be implemented only for online use, with a prompt being a singlefield.

An offline password may be implemented for offline authentication forthose applications 610 for which offline use is permitted via enterprisepolicy. For example, an enterprise may want StoreFront to be accessed inthis manner. In this case, the client agent 604 may require the user toset a custom offline password and the AD password is not used. Gatewayserver 606 may provide policies to control and enforce passwordstandards with respect to the minimum length, character classcomposition, and age of passwords, such as described by the standardWindows Server password complexity requirements, although theserequirements may be modified.

Another feature relates to the enablement of a client side certificatefor certain applications 610 as secondary credentials (for the purposeof accessing PKI protected web resources via the application managementframework micro VPN feature). For example, an application may utilizesuch a certificate. In this case, certificate-based authentication usingActiveSync protocol may be supported, wherein a certificate from theclient agent 604 may be retrieved by gateway server 606 and used in akeychain. Each managed application may have one associated clientcertificate, identified by a label that is defined in gateway server606.

Gateway server 606 may interact with an Enterprise special purpose webservice to support the issuance of client certificates to allow relevantmanaged applications to authenticate to internal PKI protectedresources.

The client agent 604 and the application management framework 614 may beenhanced to support obtaining and using client certificates forauthentication to internal PKI protected network resources. More thanone certificate may be supported, such as to match various levels ofsecurity and/or separation requirements. The certificates may be used bythe Mail and Browser managed applications, and ultimately by arbitrarywrapped applications (provided those applications use web service stylecommunication patterns where it is reasonable for the applicationmanagement framework to mediate https requests).

Application management client certificate support on iOS may rely onimporting a public-key cryptography standards (PKCS) 12 BLOB (BinaryLarge Object) into the iOS keychain in each managed application for eachperiod of use. Application management framework client certificatesupport may use a HTTPS implementation with private in-memory keystorage. The client certificate will never be present in the iOSkeychain and will not be persisted except potentially in “online-only”data value that is strongly protected.

Mutual SSL may also be implemented to provide additional security byrequiring that a mobile device 602 is authenticated to the enterprise,and vice versa. Virtual smart cards for authentication to gateway server606 may also be implemented.

Both limited and full Kerberos support may be additional features. Thefull support feature relates to an ability to do full Kerberos login toActive Directory (AD) 622, using an AD password or trusted clientcertificate, and obtain Kerberos service tickets to respond to HTTPNegotiate authentication challenges. The limited support feature relatesto constrained delegation in Citrix Access Gateway Enterprise Edition(AGEE), where AGEE supports invoking Kerberos protocol transition so itcan obtain and use Kerberos service tickets (subject to constraineddelegation) in response to HTTP Negotiate authentication challenges.This mechanism works in reverse web proxy (aka corporate virtual privatenetwork (CVPN)) mode, and when http (but not https) connections areproxied in VPN and MicroVPN mode.

Another feature relates to application container locking and wiping,which may automatically occur upon jail-break or rooting detections, andoccur as a pushed command from administration console, and may include aremote wipe functionality even when an application 610 is not running.

A multi-site architecture or configuration of enterprise applicationstore and an application controller may be supported that allows usersto be service from one of several different locations in case offailure.

In some cases, managed applications 610 may be allowed to access acertificate and private key via an API (example OpenSSL). Trustedmanaged applications 610 of an enterprise may be allowed to performspecific Public Key operations with an application's client certificateand private key. Various use cases may be identified and treatedaccordingly, such as when an application behaves like a browser and nocertificate access is required, when an application reads a certificatefor “who am I,” when an application uses the certificate to build asecure session token, and when an application uses private keys fordigital signing of important data (e.g. transaction log) or fortemporary data encryption.

Authenticating a Client Device

FIG. 7A illustrates an example method of registering a client device 702in accordance with one or more illustrative aspects described herein.The client device 702 may comprise any of the client devices previouslydescribed, such as terminals 240, client computers 411-414, mobiledevice 502, or mobile device 602. The client device 702 may also includean application (illustrated as App N), such as the client agent 604 orany other managed and/or trusted application. The server 704 illustratedin FIG. 7A may comprise any of the servers previously described, such asthe computing device 201, server 206, virtualization server 301,management server 410, enterprise resources 504, enterprise services508, access gateway 560, or gateway server 606. The database 706illustrated in FIG. 7 may comprise any of the databases and/or storagedevices previously described. In some aspects, the database 706 maycomprise long-term, persistent storage. The database 706 may comprise adevice separate from the server 704 or may be integrated in the server704.

In step 712, the client device 702 may be deployed (e.g., activated) andsend a logon request to the server 704. For example, the registrationsteps illustrated in FIG. 7A may be initiated after an application, suchas a mobile application, is installed on the client device 702. To logon, the client device 702 may send user credentials (e.g., username andpassword, PIN, account number, etc.) to the server 704, and the server704 may authenticate the client device 702 based on the usercredentials. If the client device 702 is logged on in step 712, themethod may proceed to step 714.

In step 714, the server 704 may send, to the client device 702, itspolicies for accessing services provided by the server 704 and a publickey of the server 704, such as a cryptographic public key. The clientdevice 702 may receive the public key of the server 704 and store it inmemory.

In step 716, the client device 702 may send, to the server 704, a publickey of the client device 702, such as a cryptographic public key. Inother words, the client device 702 and server 704 may exchange publickeys used to decrypt exchanged data. The server 704 may receive andstore the received public key.

In steps 718 and 720, credentials, such as a PIN, passcode, biometrics,smartcard credentials, or any other type of credential, may be createdfor a user of the client device 702. A PIN may be created each time theuser desires to create a PIN, whether for the first time or the userchanges the PIN.

FIG. 7B illustrates an example method of creating a PIN on the clientdevice 702 in accordance with one or more illustrative aspects describedherein. The CreatePin( ) function illustrated in FIG. 7B may also beused to generate an encrypted data blob and to send the encrypted datablob to the server 704, as will be described in further detail belowwith respect to step 722.

With brief reference back to FIG. 7A, in step 720, the client device 702may prompt the user to enter a PIN, such as a four or six digit PIN. Theuser may be prompted to enter the PIN twice in order to confirm thechosen PIN. In step 722, the client device 702 may generate an encrypteddata blob to send to the server 704. Returning to FIG. 7B and withreference to element 718B, the data blob may include a user ID (e.g., ausername, user account number, etc.) and/or a device ID (e.g., a MACaddress, a serial number, an IMEI number, etc.). The data blob may alsoinclude a random or pseudorandom number, which is referred to as “salt”in the pseudo code illustrated in FIG. 7B. The random or pseudorandomnumber may be, for example, 128 bytes long.

With reference to element 718A, the data blob may also include timedata, which may be used to generate a time-limited ticket or key, aswill be described in further detail in the examples below. In someaspects, the time data may comprise a tick count of a processor of theclient device 702. For example, the time data may comprise a maximumtick value (e.g., the value at which the processor tick count will rollover), a conversion of the number of ticks to seconds (e.g., the ticksper second), and the current processor tick count. The client device 702may use the processor's tick count rather than the device's clock timebecause the time can easily be modified on some devices and are thusless secure.

In step 722A (and similarly step 722 illustrated in FIG. 7A), the clientdevice 702 may encrypt the data blob, including the user's PIN, themetadata identifying the client device and/or user, and the time data.The data blob may be encrypted using the server's public key. In step722B, the client device 702 may send the encrypted data blob to theserver 704 via TLS, SSL, or any other encryption protocol. The clientdevice 702 may also securely clear from its memory (e.g., scrub oroverwrite) the PIN and/or the data blob by calling, for example, theSecureZeroMemory( ) function or any other function to securely removethe PIN and/or the data blob from memory.

With brief reference back to FIG. 7A, in step 724, the server 704 mayreceive the encrypted data blob from the client device 702. In responseto receiving the data, the server 704 may perform various processes onthe data. FIG. 7C illustrates an example method of the server 704receiving the encrypted data and processing it in accordance with one ormore illustrative aspects described herein.

In step 724A, the server 704 may retrieve its private key and decryptthe encrypted data blob with the private key to access the data blob. Aspreviously described, the data 724B may include a user ID, a device ID,a PIN, a maximum tick value, a ticks to second ratio, and/or a currentprocessor tick count. In step 724C, the server 704 may store one or morepieces of the information in the database 706. The server 704 may alsosecurely clear from its memory the user's encrypted PIN and/or theserver's private key.

Returning to FIG. 7A, in steps 726, 728, 730, and 732, the server 704may generate a signed expiration ticket for the client device 702. Theexpiration ticket may comprise static server entropy generated by theserver 704 for the client device 702. In step 728, the server 704 maystore, in the database 706, the static entropy with additional clientdevice metadata. The metadata may comprise information identifying theclient device 702, such as the user ID and/or device ID. The staticentropy may be the same for all expiration tickets belonging to aspecific client device, such as client device 702. In other words, theserver 704 may generate the static entropy once for a particular clientdevice, for the life of the client device. The server 704 may alsoencrypt and send the static entropy to the client device 702 (notillustrated).

The expiration ticket may also comprise dynamic, time-limited serverentropy generated by the server 704 for the client device 702. In step726, the server 704 may store the dynamic entropy with client metadatain database 706. The time-limited server entropy may change each time anew expiration ticket is created. In some aspects, unlike the staticserver entropy, the time-limited server entropy is not stored on theclient device 702. Instead, it may be fetched from the server 704 (orfrom a paired device, as described later) and immediately erased by theclient device 702 after each use.

The expiration ticket may also comprise a key derivation function (KDF)that uses the PIN, the static entropy, and the dynamic entropy to createcryptographic keys. The cryptographic keys may be used to encrypt theuser's PIN and encrypt the static server entropy. In step 730, theserver 704 may optionally store additional data in the database 706,including, for example, additional device identifying information suchas information identifying the user or owner of the client device 702,the time the client device 702 was registered (e.g., enrolled), and/oradditional audit data.

In step 732, the server 704 may generate the signed expiration ticket.FIG. 7D and FIG. 7E illustrate an example method of creating anexpiration ticket in accordance with one or more illustrative aspectsdescribed herein. The server 704 may call theCreateSigned-expiration-ticket( ) function to generate the ticket.Inputs to this function may include the user ID, the device ID, the PIN,the maximum tick value, the ticks per second, and/or the current tickvalue.

In some aspects, the CreateSigned-expiration-ticket( ) function may becalled each time the client device 702 (or any other client device)requests a signed expiration ticket from the server 704, including aftera hard authentication by the client device 702. A hard authenticationmay comprise verification of a username and password, and optionally atwo-factor authentication code. With reference to FIG. 7D, in step 732A,the server 704 may generate a random number using a random numbergenerator. The random number may comprise 64 cryptographically randombytes from a Federal Information Processing Standard Publication Series(FIPS) random number generator module. Other exemplary random numbergenerators that may be used include the Mersenne Twister random numbergenerator and the arc4random random number generator. The server 704 mayset the generated random number as the dynamic, time-limited serverentropy.

In step 726A (and similarly step 726 illustrated in FIG. 7A), the server704 may store the time-limited server entropy in the database 706. Theentropy may be stored with the user ID, device ID, and/or any otherinformation identifying the client device 702.

In step 732B, the server 704 may request and receive, from the database706, the static server entropy for the client device 702, which may havepreviously been generated and stored in the database 706. If, on theother hand, the server determines, in step 732C, that static serverentropy for the client device 702 is not stored in the database 706, theserver 704, in step 732D, may generate the static entropy. For example,this might be the first time that the client device 702 has requested asigned expiration ticket and static entropy has not yet been generated.In step 728A (and similarly in step 728 illustrated in FIG. 7A), theserver 704 may store the static server entropy in the database 706. Theentropy may be stored with the user ID, device ID, and/or any otherinformation identifying the client device 702.

In step 732E, the server 704 may generate an encryption key for thestatic entropy. For example, the server 704 may use a key derivationfunction (KDF), such as Password-Based Key Derivation Function 2(PBKDF2). Inputs to the KDF may include the number of KDF rounds toperform (e.g., 100,000 rounds), the PIN, and/or the time-limited serverentropy. In other words, the key for the static entropy may be based onthe time-limited entropy. The number of rounds of the key derivationfunction is variable and can be more or less than 100,000 rounds.

FIGS. 7D and 7E illustrate an example where the user is authenticatedusing a PIN. The static entropy is encrypted by a key generated byinputting both the PIN and time-limited server entropy into the KDF.Thus, the static entropy would be decrypted using a key generated basedon both the PIN and time-limited server entropy, as illustrated in thefollowing portion of pseudo code.

key-for-static-entropy = KDF(entered-pin, time-limited-server-entropy)static-entropy = Decrypt(key-for-static-entropy,encrypted-static-entropy)

In alternative aspects, the user may be authenticated without having toenter a PIN. To create the static entropy without requiring the user toenter a PIN, the server 704 may execute the KDF based on thetime-limited server entropy, but not the PIN. Thus, the static entropywould be decrypted using a key generated based on the time-limitedserver entropy, but not the PIN, as illustrated in the following portionof pseudo code.

key-for-static-entropy = KDF(time-limited-server-entropy) static-entropy= Decrypt(key-for-static-entropy, encrypted-static-entropy)

There is a security tradeoff between using a PIN and not using a PIN. Aswill be described in further detail below, additional layers of securitymay be used in the PIN-less case. For example, the client device 702 maybe required to be within communication range of a paired device, such asa mouse, or other device registered with the server 704 in order toauthenticate. Returning to the example where the PIN is used (FIG. 7D),the server 704, in step 732F, may generate an encryption key for theuser's PIN, such as by using PBKDF2. Exemplary inputs to the KDF for thePIN encryption key may include the number of KDF rounds to perform(e.g., 100,000 rounds), the time-limited server entropy, and/or thestatic server entropy. Accordingly, the key for the static entropy andthe key for the PIN may be different, and encrypted data sent to theclient device 702 may consequently be different. Moreover, by using bothtime-limited entropy and static entropy for the key for the PIN, theinput to the KDF may be longer and consequently harder to break. Otherexamples of KDFs that the server 704 may use to generate keys for thestatic entropy and/or PIN may include, for example, the Unix crypt( )function, the bcrypt( ) function, the scrypt( ) function, the HMAC-basedExtract-and-Expand Key Derivation Function (HKDF), etc.

In step 732G, the server 704 may encrypt each of the user's PIN and thestatic entropy using the generated encryption keys. The server 704 mayuse conventional encryption standards, including for example, theAdvanced Encryption Standard. Inputs to the encryption algorithm forencrypting the PIN include the PIN and the encryption key for the PIN.Inputs to the encryption algorithm for encrypting the static entropyinclude the static entropy data and the encryption key for the staticentropy. The time-limited server entropy and the static entropypreviously described may be stored in secure memory, such as in thedatabase 706. The server 704 may also securely clear from its memory thekey for the static entropy and the key for the user's PIN.

FIG. 7E illustrates a continuation of the example method of creating theexpiration ticket in FIG. 7D in accordance with one or more illustrativeaspects described herein. The server 704 may determine whether theexpiration time for the time-limited server entropy has expired. In step732H, the server 704 may determine the current time at the server (e.g.,nowTime). In some aspects, the server 704 may use a particular time zoneas the base time to avoid time zone issues. For example, the server 704may use the Greenwich Mean Time (GMT).

The server 704 may also calculate an expiration time, such as the timethat a client device PIN validator will expire at the client device. Theexpiration time may be based on an expiration policy, which may be setby an administrator. The server 704 may input the current time (e.g.,nowTime) into the CalculateExpirationTimeFrom( ) function to calculatethe expiration time (e.g., expirationTimeSeconds).

In step 732I, the server 704 may calculate the amount of time betweenthe current time and the expiration time of the ticket (e.g., thelifetimeSeconds). If the server 704 uses the client device's tick value(rather than time value), the server 704, in step 732J, may calculatethe expiration tick count (e.g., tickEnd). For example, the server 704may input the lifetimeSeconds value, the tickRollover value, thetickPerSecond value, and the tickNow value into a function used tocalculate the expiration tick count. The expiration tick count maycomprise the expected tick count at the client device 702 when theticket expires.

As an example for calculating the expiration tick count (e.g., tickEnd),assume that the lifetimeSeconds value is 50, the tickRollover value is1000, the tickPerSecond value is 10, and the tickNow value is thecurrent tick value (e.g., TNow). The lifetimeSeconds may be converted toticks (e.g., 50 lifetimeSeconds×10 tickPerSecond=500 ticks). Thisexample is illustrated in the following diagram.

-   0|-------------TNow-------------|1000

If TNow is less than 500, then step 814D (as will be described below) istrue, and tickStart has a lower value than tickEnd, as illustrated inthe following diagram.

-   0|--tickStart--------tickEnd----|1000-   0|-------------TNow-------------|1000

Accordingly, the algorithm determines whether TNow is in between thetick start and tick end values. If not, then TNow is either greater thantickEnd or less than tickStart (e.g., step 814E, as will be describedbelow, is true). On the other hand, if TNow is greater than or equal to500, TNow will wrap around tickRollover, as illustrated in the followingdiagram.

-   0|------tickEnd--tickStart-------|1000-   0|-TNow------------------Tnow-|1000

If there is a wrap around, TNow is still “between” the tickStart andtickEnd values. However, due to the wrap around, TNow is greater thantickStart or less than tickEnd, and step 814F is false, as will bedescribed below. One reason for computing the expiration tick count(rather than using the expiration time value in seconds) is to ensurethat the client device 702 cannot simply reset the local time value toartificially increase the time in which a ticket is valid. This securityfeature may be used because the tick count at the processor of theclient device 702 may constantly be increasing until the tick countwraps around to zero (e.g., reaches the maximum tick value ortickRollover).

In step 732K, the server 704 may generate a time-based validator, suchas a PIN validator (e.g., timeBasedPinValidator), by encrypting one ormore of the information previously described. For example, the servermay encrypt the expiration time at the client device 702 when PINvalidator expires (in seconds), the tick count at the processor of theclient device 702 when the PIN validator expires (and similarly the tickcount at the processor of the client device 702 when the PIN validatorwas created), the encrypted PIN, the encrypted static entropy, and/orthe KDF used to generate one or more encryption keys. The time-based PINvalidator may be encrypted using the public key of the client device702. In step 732L, the server 704 may also save one or more of thisinformation to the database 706, in association with a client deviceidentifier, such as the user's ID or the client device's ID.

In step 732M, the server 704 may retrieve the server's private key andsign the time-based PIN validator using the server's private key. Theencrypted and signed PIN Validator may be referred to as a signedexpiration ticket which may be the PIN validator which consists of thedata the client device 702 uses to construct and/or compute the PINvalidation function. The CreateSigned-expiration-ticket( ) illustratedin FIGS. 7D and 7E may return the signed expiration ticket to the server704. Returning to FIG. 7A, the server 704 may send the signed expirationticket to the client device 702 in step 734 (and similarly in step 734Aillustrated in FIG. 7C).

In some aspects, the PIN validator at the client device 702 may checkone or more of the client device time and a tick count at the processorof the client device to determine whether the PIN validator has expired.The server 704 may also enforce the expiration time in parallel beforethe server 704 sends the time-limited server entropy to the clientdevice 702. The purpose of the client device 702 also checking is toavoid unnecessary round-trip communication with the server 704.

FIG. 8A illustrates an example method of validating a client device 702identifier, such as the PIN, in accordance with one or more illustrativeaspects described herein. For example, the method may comprise a PINvalidation procedure, and PIN validation may occur if the trusted App onthe client device 702 authenticates the user of the client device 702 bychallenging the user to enter the correct PIN.

In step 812, the client device 702 may verify the signature of thesigned expiration ticket in response to receiving the ticket from theserver 704. FIG. 8B illustrates an example method of a client devicereceiving an expiration ticket (and verifying the signature) inaccordance with one or more illustrative aspects described herein.

In some aspects, the client device 702 may verify the signature eachtime the client device 702 performs a hard authentication with theserver 704 to obtain a new expiration ticket. In step 812A, the clientdevice 702 may retrieve the server's public key, which may havepreviously been stored by the client device 702. In step 812B, theclient device 702 may verify the signature of the signed expirationticket using the server's public key. If the signature cannot beverified, the client device 702 may display an error and optionallydiscard the data. If the expiration ticket's signature is valid, theclient device 702 may decrypt the timed-based PIN validator using theclient device's private key in step 814 (illustrated in FIG. 8A). Theclient device 702 may optionally store the signed expiration ticket instep 812C.

FIGS. 8C and 8D illustrate an example method of verifying a PIN inaccordance with one or more illustrative aspects described herein. TheReceive-signed-expiration-ticket( ) function illustrated in FIG. 8B maybe included in the VerifyPin( ) function illustrated in FIG. 8C. Themethod illustrated in FIGS. 8C and 8D may be used to verify the user'sentered PIN on the client device 702 and may be called each time the PINis to be verified. As will be explained below, if PIN verification issuccessful, static server entropy may be returned, and the static serverentropy may be optionally used (depending on policy) to create one ormore keys to unlock one or more secure vaults, such as vaults 616.

With reference to FIG. 8C, in step 812D, the client device 702 may reset(e.g., set to false) the trigger indicating that the entered PIN iscorrect (e.g., correctPin). The client device 702 may also retrieve theserver's public key and the signed expiration ticket. In step 812B, theclient device 702 may verify the signature of the signed expirationticket by calling the VerifySignature( ) function and inputting theserver public key, as previously explained. If the signature cannot beverified, the client device 702 may display an error and optionallydiscard the data. The client device 702 may also instruct the user toperform a hard authentication with the server 704. By verifying thesignature of the expiration ticket, the client device 702 may preventthe expiration ticket from being tampered with, such as on a jail brokendevice. In step 814A (and similarly step 814 illustrated in FIG. 8A), ifthe expiration ticket's signature is valid, the client device 702 mayretrieve the client device's private key and use it to decrypt theexpiration ticket to obtain the time-based PIN validator.

Once the client device 702 has access to the time-based PIN validator,the client device 702 may determine whether the expiration ticket hasexpired. In step 814B, the client device 702 may determine the currentdevice time in seconds (e.g., deviceTimeSeconds) and the current tickcount of the client device processor (e.g., tickNow). The client device702 may also read time or tick data from the expiration ticket,including the tick start count (e.g., tickStart) and/or the tick endcount (e.g., tickEnd). The client device 702 may also access theencrypted PIN (e.g., encryptedPin) and/or the encrypted static serverentropy (e.g., encrypted-static-entropy).

In step 814C, the client device 702 may determine whether the currentdevice time is greater than or equal to the expiration time. If so, theticket has expired, and the client device 702 may return an error andinstruct the user to perform a hard authentication with the server 704.If not, the client device 702, in step 814D, may determine whether thetick start count is less than the tick end count. If so, the clientdevice 702 may determine, in step 814E, whether (1) the tick end countis less than or equal to the current tick count or (2) the current tickcount is less than or equal to the tick start count. In either case (1)or (2), the client device 702 may determine that the tick count hasrolled over and accordingly that the ticket has expired. The clientdevice 702 may return an error and instruct the user to perform a hardauthentication with the server 704.

With reference to FIG. 8D, if neither case (1) nor case (2) is true, theclient device 702 may determine, in step 814F, whether the tick endcount is less than or equal to the current tick count and the currenttick count is less than or equal to the tick start count. If so, theclient device 702 may determine that the tick count has rolled over andaccordingly that the ticket has expired. The client device 702 mayreturn an error and instruct the user to perform a hard authenticationwith the server 704. If either the tick end count is greater than thecurrent tick count or the current tick count is greater than the tickstart count, the client device 702 may determine that the ticket has notexpired and proceed to step 816 illustrated in FIG. 8A.

In step 816, the client device 702 may create a signed-user-device-IDrequest. This request may comprise the user's ID and/or the clientdevice ID. In step 818 (and similarly step 818A illustrated in FIG. 8D),the client device 702 may digitally sign the request using the clientdevice's private key and send the signed request to the server 704. Inother words, the client device 702 may send a request to the server 704to fetch the time-limited server entropy for the client device 702. Thetime-limited server entropy, once received, may be used to decrypt thecorrect PIN in order to validate the PIN entered by the user. If theclient device 702 encounters errors in communicating with the server 704during the PIN validation process, the client device 702 may instructthe user to perform a hard authentication with the server 704.

In step 820, the server 704 may receive the signed request for thetime-limited server entropy. FIG. 8E illustrates an example method ofthe server 704 handling a client request for time-limited entropy inaccordance with one or more illustrative aspects described herein.

In step 820A, the server 704 may compare the current time to theexpiration time of the time-limited ticket, which may be stored in thedatabase 706. The time-limited ticket may be identified using the userID and/or the client device ID. If the current time is greater than orequal to the expiration time of the ticket, the server 704 may determinethat the ticket has expired, return an error, and request the user toperform a hard authentication with the server 704 (e.g., using theuser's username, password, and optionally two-factor authenticationcode).

If the ticket has not expired, the server 704, in step 820B, may attemptto validate the digital signature on the request. In particular, theserver 704 may obtain the public key of the client device 702 using theuser ID and/or the client device ID. If the signature on the request isinvalid, the server 704 may return an error and request the user toperform a hard authentication with the server 704. On the other hand, ifthe signature on the request is valid, the server 704, in step 822A (andsimilarly step 822 illustrated in FIG. 8A), may request the time-limitedserver entropy from the database 706.

Returning to FIG. 8A, in step 824, the database 706 may return thetime-limited server entropy to the server 704. In step 826 (andsimilarly step 826A illustrated in FIG. 8E), the server 704 may encryptthe entropy using the client device's public key and send thetime-limited entropy to the client device 702. For example, thetime-limited entropy may be secured using TLS or SSL.

In another example, the client device 702 may store (e.g., cache) thetime-limited server entropy. Caching may be allowed based on policyconfiguration as a trade-off between security and usability. If theclient device 702 caches the time-limited server entropy, then PINvalidation could be performed offline (e.g., without connectivity to theserver 704). The cache expiration time may be determined based on afixed time period, a client application lifetime, and/or a period ofuser inactivity. The cached time-limited server entropy may be encryptedwith the public key of the client device 702, as it was received fromthe server 704. Additionally or alternatively, the cached time-limitedserver entropy may be encrypted with a user credential, such as the PIN.In these examples, the client device 702 may fetch the cachedtime-limited server entropy in response to receiving the usercredential, rather than sending a request for the time-limited serverentropy to the server 704.

In step 828, the client device 702 may decrypt the received time-limitedserver entropy using the client device's private key. For example andwith reference to FIG. 8D, in step 828A, the client device 702 may usethe time-limited server entropy and the entered PIN to derive acryptographic key for the static entropy using a key derivationfunction, such as PBKDF2. The client device 702 may input the number ofKDF rounds (e.g., 100,000), the PIN entered by the user, and thetime-limited server entropy received from the server 704 into thePBKDF2( ) function illustrated in FIG. 8D. In step 828B, the clientdevice 702 may use the key to decrypt the static entropy previouslyreceived as part of the PIN Validator from the server 704. As previouslyexplained, the static server entropy may have been encrypted using thetime-limited server entropy and may be accessed by the client device 702if the expiration time has not been reached. In step 828C, the clientdevice 702 may use the static entropy and the time-limited entropy toderive another cryptographic key, e.g., a key used to unlock the PIN,using a KDF. For example, the key derivation function for determiningthe key for the PIN may also comprise the PBKDF2( ) function. In step828D, the client device 702 may use the derived key for the PIN todecrypt the encrypted PIN.

In step 830A (and similarly step 830 illustrated in FIG. 8A), the clientdevice 702 may compare the decrypted PIN with the PIN entered by theuser. If the PINs do not match, the client device 702 may prompt theuser to reenter the user's PIN. The procedure may be repeated, and keymaterial may be scrubbed from the client device's memory. For example,the client device 702 may call again the VerifyPin( ) functionillustrated in FIGS. 8C and 8D. The client device 702 and/or server 704may count the number of retries performed by the user. If the number ofretries exceeds a threshold, the client device 702 and/or server 704 mayrequest the user to perform a hard authentication. If, on the otherhand, the PINs match, the client device 702 may use the static entropyto decrypt additional keys and/or cryptographic vaults (e.g., vaults616) on the client device 702. The vaults may comprise additionalsensitive data, such as additional authentication keys, passwords,cookies, session tickets, inactivity timers, and other data protected bymanaged applications.

The foregoing validation processes have several security properties thatmay be beneficial if the user's client device 702 is stolen ormisplaced. Sensitive data stored in the vault(s) cannot be decrypted andaccessed because the time-limited server entropy might not be written tomemory of the client device 702 and may be scrubbed from memory aftereach use. Accordingly, a thief is not able to recover the key for thestatic entropy, which is encrypted using the time-limited serverentropy. Furthermore, the static entropy might not be written to memoryof the client device 702 in clear. Rather, the static entropy may beencrypted with keys derived from the PIN and/or the time-limited serverentropy. Accordingly, the encrypted static server entropy may be safelystored in either program memory or on a disk of the client device 702.The encryption keys, on the other hand, might not be stored on the diskand might be temporarily stored in program memory of the client device702 and cleared from the memory after use. Thus, if the client device702 is stolen, and the device's disk is read, the key to decrypt thevault(s) cannot be found in memory. Moreover, the KDF is configurableand may be modified, strengthened, or changed over time. The KDF may beconfigured so that the time-limited server entropy is valid for lessthan the expected time for a thief to run a brute force attack on theKDF function, using the data that could be recovered from a stolenclient device 702. Moreover, users' PINs might not be stored in arecoverable form on the server 704. Thus, an attacker who breaks intothe server 704 cannot read users' PINs.

In the examples illustrated in FIGS. 7 and 8, the client device 702obtains the time-limited server entropy from the server 704 in order toaccess vault keys. In these examples, the client device 702 would haveto be connected to the server 704 (e.g., via the Internet), whenever theuser desires to authenticate with the user's PIN. As will be describedbelow, users may alternatively authenticate using an authenticationproxy, such as a paired device, if the client device 702 cannot connectto the server 704. Accordingly, users may use software in a protectedvault even if Internet connectivity is not available.

FIG. 9 illustrates an example method of registering a paired device 708for authenticating the client device 702 in accordance with one or moreillustrative aspects described herein. As will be described below, thepaired device 708 may be used to authenticate the client device 702 ifthe server 704 is not available. As such, the paired device 708 mayserve as a proxy for the server 704. The paired device 708 may compriseany device that can be registered and/or authenticated with the server704. In some aspects, the paired device 708 may be paired with anotherdevice, such as the client device 702, and/or with a particular user,such as the user of the client device 702. Exemplary paired devices 708may include a mouse (e.g., the CITRIX Mouse), a smart watch, a mobilephone, a laptop computer, a desktop computer, etc. In some aspects, thepaired device 708 may be wirelessly connected, such as wirelessly pairedvia Bluetooth, near-field communication (NFC), or Wi-Fi, or wiredlyconnected, such as USB, to the client device 702. The paired device 708may also include local programmable storage.

In step 912, the device 708 may be configured with the URL of the server704. For example, the user may manually type the server URL.Alternatively, the user may click on a URL provided in an email from aserver administrator. Optionally, the user may type in a One TimePassword (OTP) provided by the administrator. Alternatively, the usermay click on a URL provided in an email from the administrator. The URLmay contain a token, which may have been associated and pre-approved bythe administrator for a specific device and user. For other devices,such as a paired mouse or smartwatch, there may be a companionapplication that the user may run to configure his or her device withthe server URL. In the case of the mouse, the companion application mayrun on a paired device 708 and proxy the communication with the server704.

In step 914, the device 708 may send a pairing request to the server704. The pairing request may include information identifying the device708 (e.g., make and model, MAC address, serial number, IP address, etc.)and information identifying the client device 702 and/or a user of theclient device 702 (e.g., username, account number, etc.). The requestmay also include an OTP.

In step 916, the server 704 may receive the pairing request and requestthat the client device 702 and/or user approve the pairing request. Forexample, the server 704 may identify the client device 702 based on theinformation included in the pairing request and send an approval requestto an application installed on the client device 702 or other deviceassociated with the user, such as a different client device. If the userapproves the pairing request, the client device 702 or other device mayrespond to the server's approval request. In some aspects, the pairingmay be approved without user input. For example, the pairing request mayinclude the user credentials (e.g., PIN, password, etc.), OTP, token,etc. Information from the BT or NFC connection between the client device702 and the paired device 708 may also be used to automatically approvethe request. A QR code may also be used to approve the request. Forexample, the server 704 may generate a QR code associated with thedevice 708 and to be displayed on the client device 702. The device 708could then scan the QR code displayed on the client device 702 using,for example, a camera. The device 708 could then send the scanned QRcode back to the server 704, thus completing the pairing request.

In step 918, the server 704 may look up or otherwise retrieve thetime-limited server entropy from the database 706 in response to thedevice 708 being approved for pairing. In step 920, the server 704 maydetermine the expiration time of the time-limited server entropy. Theserver may also encrypt the time-limited server entropy with the publickey of the client device 702. The server 704 may send the time-limitedserver entropy and the expiration time of the time-limited serverentropy to the paired device 708. In some aspects, the time-limitedserver entropy may be encrypted, whereas the expiration time might notbe encrypted. Because the time-limited server entropy is encrypted withthe public key of the client device 702, the paired device 708 might notbe able to read the time-limited server entropy. The expiration time, onthe other hand, may be sent in clear (e.g., without encryption using theclient device's key, but optionally signed by the server 704) so thatthe paired device 708 can read the expiration time.

The paired device 708 may locally store the encrypted time-limitedserver entropy and the expiration time, for future use by the clientdevice 702. The paired device 708 may wait for a request from the clientdevice 702 (or another device) to use the time-limited server entropy.The client device 702 accessing the time-limited server entropy storedon the paired device 708 will be described in further detail below withreference to FIGS. 10 and 11.

In step 922, the paired device may check (e.g., periodically oroccasionally) whether the time-limited server entropy has expired bycomparing the current time to the expiration time. If the time-limitedserver entropy has not expired, the paired device 708 may continue towait for a request from the client device 702 to use the time-limitedserver entropy. If the time-limited server entropy has expired, thepaired device 708 may again request the time-limited server entropy fromthe server 704 in step 924. In step 926, the server 704 may optionallyobtain an approval from the user to provide the paired device 708 withthe time-limited server entropy. The server 704 can be configured torequest user approval for each pairing request, for the first pairingrequest, or via a configurable frequency (e.g., every other pairingrequest, every fourth pairing request, etc.).

In step 928, the server 704 may access the time-limited server entropyfrom the database 706. In step 930, the server 704 may determine the newexpiration time of the time-limited server entropy, such as via a server(administrative) policy. The paired device 708 may query the server 704once the expiration time of the current time-limited server entropy isreached. The server 704 may also encrypt the time-limited server entropywith the public key of the client device 702 and send the encryptedentropy and the new expiration time to the paired device 708. The paireddevice 708 may store the time-limited server entropy for future use bythe client device 702. As previously explained, the paired device 708may periodically or occasionally check whether the time-limited serverentropy has expired.

FIG. 10 illustrates an example method of authenticating a client device702 using a paired device 708 in accordance with one or moreillustrative aspects described herein. In step 1012 (and similar to step818), the client device 702 may attempt to send a request to the server704 for the time-limited server entropy. However, the client device 702might not receive a response to the request from the server 704 anddetermine, in step 1014, that the server 704 is offline or otherwiseunreachable (e.g., a connection between the client device 702 and theserver 704 cannot be established).

In response to determining that the server 704 is offline or otherwiseunreachable, the client device 702, in step 1016, may determine whetheranother device, such a local device and/or a device connected to theclient device 702, is reachable and/or has the time-limited serverentropy. Alternatively, the client device 702 may attempt to obtain thetime-limited entropy from the paired device 708 without firstdetermining that the entropy cannot be obtained from the server 704. Ifthe client device 702 identifies the paired device 708, the clientdevice 702 may send, in step 1018, a request for the time-limited serverentropy to the paired device 708. In step 1020, the paired device 708may optionally receive, from the user, approval of the request for thetime-limited server entropy. For example, the user may approve therequest by pressing a physical or touchscreen button on the paireddevice 708, entering credentials for signing on to the server 704,paired device 708, and/or the client device 702, or providing otherinput indicating approval. Once approved, the paired device 708, in step1022, may send the time-limited server entropy to the client device 702.As previously explained, the time-limited server entropy may beencrypted with the public key of the client device 702, and the paireddevice 708 might not have access to the entropy because it does not havethe corresponding private key to decrypt the entropy. In other words,the paired device 708 may pass along an encrypted opaque value that thepaired device 708 cannot itself interpret, read, and/or decrypt.

As previously explained with reference to FIG. 8A, the client device 702may decrypt the encrypted time-limited server entropy and use it todecrypt the static entropy, similar to step 828 illustrated in FIG. 8A.The client device 702 may further decrypt the encrypted PIN stored atthe client device 702 and compare the PIN to the PIN entered by theuser, similar to step 830 illustrated in FIG. 8A. If the PINs match, theclient device 702 may be granted access to additional sensitive data,such as data held in a vault at the client device 702.

Authentication without using a PIN was previously described withreference to FIGS. 7A, 7D, and 7E. Like PIN-less authentication usingthe server 704, PIN-less authentication may also be used whenauthenticating the client device 702 using the paired device 708. Forexample, the key for the static entropy may be generated using thetime-limited server entropy, but not a PIN. Accordingly, the clientdevice 702 may decrypt the static entropy using the time-limited serverentropy received from the paired device 708, but not the PIN.

There is a security tradeoff between using a PIN and not using a PIN. Athief may be able to decrypt secure vaults without knowing the user'sPIN. However, the paired device 708 may add additional layers ofsecurity in the PIN-less case (and similarly in the case using a PIN).For example, a thief that steals the client device 702 would not be ableto access the time-limited entropy stored in the paired device 708 ifthe client device 702 is outside the communication range of the paireddevice 708. Accordingly, local communication network protocols havingshorter communication ranges, such as Bluetooth or NFC, may be used foradded security. The thief would have to steal both the client device 702and the paired device 708 in order to decrypt the secured vaults.Moreover, the application policies can define the period of time aclient device 702 may be able to fetch the time-limited server entropyfrom the paired device 708 and how long the entropy can be used.

Aspects described herein may be used for single sign-on (SSO) of theuser over multiple devices. In other words, the data stored in encryptedvaults of a first device may be shared with other devices in the user'scontrol. This allows the user to seamlessly roam between devices and nothave to re-authenticate connections and applications when switching fromone device to another.

FIG. 11 illustrates an example method of a first device 702 sharingsensitive data with a second device 710 via a paired device 708 inaccordance with one or more illustrative aspects described herein. FIG.12 illustrates an example method of the first device 702 sharingsensitive data with the second device 710 via a server 704 in accordancewith one or more illustrative aspects described herein. In some aspects,the first device 702 may share sensitive data with the second device 710via the paired device 708 if the first or second device determine thatthe server 704 is unavailable (e.g., the connection between the firstdevice 702 and the server 704 and/or the connection between the seconddevice 710 and the server 704 cannot be established). In other aspects,sensitive data may be shared via the paired device 708 without firstmaking a determination that the server 704 is unavailable. FIGS. 11 and12 will now be described together.

The application on the first device 702 may provide a way for the userof the first device 702 to access resources on the server 704, such asbrowsing corporate intranet resources using a web browser. The firstdevice 702 may access these resources via a VPN connection, such asMicroVPN connection, to the server 704. In some aspects, the server 704may act as a proxy allowing the web browser to access intranet resourcesvia HTTP or HTTPS. As previously explained, the first device 702 mayhave vaults 616 that store sensitive data, such as authenticationtickets or cookies used by the first device 702 to connect to a VPNendpoint. The vault may be encrypted by a vault encryption key that isderived from static entropy. In some aspects, accessing VPNauthentication tickets may require full authentication using, forexample, the user's username, password, and optionally a two-factorauthentication code. From a user experience perspective, it would beadvantageous to allow VPN authentication tickets to follow a user as theuser switches from one device to another device.

As a brief example, assume that a managed application browser is openedon a small screen device such as a phone, and the user is reading a longdocument available via the intranet (e.g., athttp://internal.company.tld/). The user may want to switch from thesmall screen device to a larger screen device, such as a tablet, tobetter read the document. Single sign-on to the tablet may be achievedif the VPN authentication tickets stored at the phone follow the userfrom the phone to the tablet. This would allow the user to instantlyopen the managed application browser without having to enter fullauthentication credentials. Inactivity timers at the phone may alsofollow the user to the tablet because the user is still active on themanaged application.

With reference to FIGS. 11 and 12, data (e.g., VPN authenticationtickets, inactivity timer, and/or other sensitive data) can be sharedbetween two managed applications, such as App 1 on the first device 702and App 2 on the second device 710 in two different ways. In FIG. 11,the data may be shared via the paired device 708. In this scenario, theserver 704 need not be online or available for data to be shared. Insome aspects, both the first device 702 and second device 710 maycommunicate with the paired device 708 via a short range communicationprotocol, such as Bluetooth, NFC, or Wi-Fi, or may be wiredly connectedover USB. Alternatively and in FIG. 12, the data may be shared via theserver 704.

In steps 1112 and 1212, the first device 702 may be configured with thepublic key of the second device 710. For example, the second device 710may send its public key to the first device 702 directly or through aproxy, such as the paired device 708 or the server 704. Similarly, thesecond device 710 may be configured with the public key of the firstdevice 702.

In steps 1114 and 1214, the first device 702 may encrypt the sensitivedata (e.g., VPN authentication tickets, inactivity timer, and/or othersensitive data). The first device 702 may encrypt the data with thepublic key of the second device 710. The first device 702 may also signthe data with its private key. In steps 1116 and 1216, the first device702 may send the encrypted data to the paired device 708 (FIG. 11) orthe server 704 (FIG. 12). The VPN authentication tickets may be sent(e.g., shared with the paired device 708) once available in the firstdevice 702. Alternatively, if polling is supported, the encryptedtickets may be sent on demand, and a policy may be in place to controlthat functionality. The paired device 708 or server 704 may verify thesignature of the first device 702 and store the encrypted data locallyor in a database, such as the database 706 in the case of the server 704acting as the proxy for data transfer.

In steps 1118 and 1218, the second device 710 may request the sensitivevault data from the paired device 708 (FIG. 11) or the server 704 (FIG.12). For example, the user may pick up the second device 710 and accessthe managed application, App 2, which may be the same or similar managedapplication as App 1 on the first device 702. The user may optionallysign on to the second device 710, such as by entering a PIN, password,or other credentials. The second device 710 may validate the credentialsentered by the user.

In steps 1120 and 1220, the paired device 708 (FIG. 11) or the server704 (FIG. 12) may send the encrypted vault data to the second device710. As explained above, the data may be encrypted with the public keyof the second device 710. In steps 1122 and 1222, the second device 710may receive the encrypted data. The second device 710 may decrypt thedata using its private key. The second device 710 may also sign a hashof the encrypted data with its private key. After the data is decrypted,the second device 710 may use the data to access one or more resources,such as corporate intranet resources via a VPN connection. As previouslyexplained, the inactivity timer may continue running and may be includedwith the data sent to the second device 710. Alternatively, the seconddevice 710 may initiate a new inactivity timer for the application.

In the foregoing examples, the server 704 acts as a source of entropyfor the static entropy and time-limited entropy used by the clientdevice 702. In alternative aspects, the system may use the paired device708 as an additional source of entropy. With reference to FIG. 7A (e.g.,at or about step 726), the paired device 708 may generate time-limitedpaired device entropy and send the entropy to the server 704. The paireddevice 708 may send the entropy directly to the server 704 or through aproxy, such as the client device 702. The paired device 708 may generatethe time-limited paired device entropy using, for example, a randomnumber generator at the paired device 708. The server 704 may receivethe time-limited paired device entropy and optionally store the entropyin the database 706, which may be beneficial if the paired device 708 islost.

In step 732, the server 704 may combine both time-limited entropysources to generate the expiration ticket. In particular and withreference to FIG. 7D, the server 704, in step 732E, may input both thetime-limited server entropy and the time-limited paired device entropyinto a KDF, such as PBKDF2, in order to generate the key for the staticserver entropy. The server and paired device server entropies may expireat the same time or expire at different times. The server 704, in step732F, may input both time-limited entropies (in addition to the staticserver entropy) to generate the key for the PIN, if a PIN is used.

In alternative aspects, the server 704 may use the time-limited paireddevice entropy (and not the time-limited server entropy) to generate thekeys for the static server entropy and/or the PIN. In other words, thetime-limited paired device entropy may replace the time-limited serverentropy in the foregoing examples. The server 704 may similarly replacethe static server entropy with static paired device entropy.

In some aspects, the paired device 708 may function like the server 704with respect to managing entropy and generating keys. For example, thepaired device 708 may generate its own static paired device entropy andmay generate a key for the static paired device entropy usingtime-limited paired device entropy, without involvement by the server704.

In some aspects, the client device 702 may generate entropy and keys forthe entropy on its own, without server involvement. After the initialPIN prompt during the first time use, the client device 702 may directlyuse a passphrase and the PIN to generate entropy and keys. Thepassphrase may include enough entropy to construct the encryption keys.The client device 702 may send the generated entropy and any additionalmetadata (e.g., data identifying the client device 702) to the server704 and/or database 706 for storage. After this initial modifiedbootstrapping step by the client device 702, the method may proceed asdescribed above.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are described asexample implementations of the following claims.

What is claimed is:
 1. A method comprising: receiving a request from aclient device for time-limited entropy generated by a server, whereinthe time-limited entropy comprises an expiration time, and wherein thetime-limited entropy is usable to access a static entropy generated bythe server; determining whether a current time exceeds the expirationtime of the time-limited entropy; and if the current time does notexceed the expiration time of the time-limited entropy, sending thetime-limited entropy to the client device.
 2. The method of claim 1,further comprising: if the current time does not exceed the expirationtime of the time-limited entropy, encrypting, by the server, thetime-limited entropy using a public key of the client device, whereinsending the time-limited entropy comprises sending the time-limitedentropy encrypted using the public key of the client device.
 3. Themethod of claim 1, wherein the request is received at the server, themethod further comprising: if the current time exceeds the expirationtime of the time-limited entropy, sending, by the server, a responserequesting the client device to perform a hard authentication.
 4. Themethod of claim 3, wherein the hard authentication comprises providing ausername and a password or a two-factor authentication code.
 5. Themethod of claim 1, further comprising: receiving and storing, at adevice paired with the client device, the time-limited entropy generatedby the server, wherein the request for the time-limited entropy isreceived at the device paired with the client device, and wherein thesending the time-limited entropy to the client device is performed bythe device paired with the client device.
 6. The method of claim 5,wherein the device paired with the client device comprises a mouseconnected to the client device via Bluetooth, Near Field Communication,Wi-Fi, or USB.
 7. The method of claim 1, further comprising: generating,by the server and using the time-limited entropy, a key for the staticentropy, wherein the key is usable to access the static entropy.
 8. Themethod of claim 7, further comprising: encrypting the static entropyusing the key for the static entropy; and sending the encrypted staticentropy to the client device.
 9. The method of claim 7, whereingenerating the key for the static entropy uses a passcode provided by auser at the client device.
 10. The method of claim 9, furthercomprising: generating, by the server and using the static entropygenerated by the server, a key for the passcode provided by the user.11. A method comprising: receiving, at a client device, a usercredential; in response to receiving the user credential, sending, bythe client device, a request for time-limited entropy generated by aserver, wherein the time-limited entropy expires at a predefined time;receiving, by the client device, the time-limited entropy generated bythe server; accessing, by the client device, a stored user credentialbased on the time-limited entropy generated by the server and staticentropy generated by the server; and authenticating a user of the clientdevice by comparing the received user credential to the stored usercredential.
 12. The method of claim 11, wherein accessing the storeduser credential based on the time-limited entropy and the static entropycomprises: determining a key for the static entropy based on thetime-limited entropy; decrypting the static entropy using the key forthe static entropy; determining a key for the stored user credentialbased on the decrypted static entropy; and decrypting the stored usercredential using the key for the stored user credential.
 13. The methodof claim 11, wherein accessing the stored user credential based on thetime-limited entropy and the static entropy comprises: determining a keyfor the static entropy based on the received user credential and thetime-limited entropy; decrypting the static entropy using the key forthe static entropy; determining a key for the stored user credentialbased on the time-limited entropy and the decrypted static entropy; anddecrypting the stored user credential using the key for the stored usercredential.
 14. The method of claim 11, wherein the client devicecomprises a first client device, the method further comprising afterauthenticating the user of the first client device: accessing, by thefirst client device, data stored in a secure vault; and sending, by thefirst client device, the data stored in the secure vault to a secondclient device, wherein the data stored in the secure vault is usable bythe second client device to access one or more resources accessible tothe first client device.
 15. The method of claim 11, wherein the clientdevice sends the request for the time-limited entropy to the server orto a device paired with the client device.
 16. The method of claim 11,further comprising: locally storing, by the client device, thetime-limited entropy, wherein the locally stored time-limited entropyexpires at a second predefined time; and fetching the locally storedtime-limited entropy in response to receiving the user credential. 17.The method of claim 11, further comprising: prior to sending the requestfor the time-limited entropy, determining, by the client device, thatthe time-limited entropy has not expired, wherein the request for thetime-limited entropy is sent in response to receiving the usercredential and in response to determining that the time-limited entropyhas not expired.
 18. An apparatus, comprising: a processor; and memorystoring computer-executable instructions that, when executed by theprocessor, cause the apparatus to: determine time-limited entropy for aclient device, the time-limited entropy having an expiration time;determine static entropy for the client device; generate a key for thestatic entropy using a passcode for a user of the client device and thetime-limited entropy, wherein the passcode is usable to authenticate theuser; and generate a key for the passcode using the time-limited entropyand the static entropy.
 19. The apparatus of claim 18, wherein thememory stores additional computer-executable instructions that, whenexecuted by the processor, cause the apparatus to: encrypt the staticentropy using the key for the static entropy; encrypt the passcode usingthe generated key for the passcode; and send the encrypted staticentropy and the encrypted passcode to the client device.
 20. Theapparatus of claim 18, wherein the memory stores additionalcomputer-executable instructions that, when executed by the processor,cause the apparatus to: authenticate a device paired with the clientdevice; encrypt the time-limited entropy with a key accessible by theclient device; and send the encrypted time-limited entropy and theexpiration time to the device paired with the client device.